Vehicle control apparatus

ABSTRACT

A vehicle control apparatus includes an electric control unit that performs a preceding vehicle trading control which makes an own vehicle trail a preceding vehicle as an adaptive cruise control, and performs a first brake control which automatically applies a first braking control to the own vehicle when a time-to-collision to a target object is less than a first threshold. In a case where a performing condition for the first brake control has been determined to be satisfied during a performance of the adaptive cruise control, the electric control unit continues performing the adaptive cruise control without performing the first brake control when a deceleration control by the adaptive cruise control is being performed, whereas stops performing the adaptive cruise control when the deceleration control by the adaptive cruise control is not being performed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2017-062780 filed Mar. 28, 2018, which is incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a vehicle control apparatus configuredto perform an adaptive cruise control and a pre-crash brake control.

BACKGROUND ART

A vehicle control apparatus which performs an adaptive cruise controland a pre-crash brake control has been conventionally known.Hereinafter, a vehicle in which such a vehicle control apparatus ismounted is referred to as an “own vehicle”.

The adaptive cruise control is a control to make the own vehicle travelat a predetermined constant speed when no preceding vehicle exists aheadof the own vehicle, and when there exists a preceding vehicle, toaccelerate or decelerate the own vehicle in such a manner that the ownvehicle trails the preceding vehicle, keeping a predeterminedinter-vehicular distance. Specifically, in the adaptive cruise controlwhere there exists the preceding vehicle, a target acceleration iscalculated based on a “deviation between an inter-vehicular distance tothe preceding vehicle and the predetermined inter-vehicular distance”and a “relative speed”, and the own vehicle is accelerated ordecelerated so that an acceleration of the own vehicle becomes equal tothe target acceleration. Hereinafter, the adaptive cruise control isalso referred to as an “ACC”.

On the other hand, the pre-crash brake control is performed by a vehiclecontrol apparatus where a pre-crash safety system (PCS) is adopted. Thepre-crash brake control is a control to automatically generate a brakingforce when there exists a target object with a high probability ofcolliding with the own vehicle. Specifically, a time-to-collision (TTC)to a target object (a vehicle, a pedestrian, and a bicycle) iscalculated based on a distance to this target object and a relativespeed, and when the time-to-collision is less than or equal to a timethreshold, the braking force is generated. Hereinafter, the pre-crashbrake control is also referred to as a “PCBC”.

One of prior art control apparatuses (hereinafter, referred to as a“prior art apparatus”) capable of performing both of the ACC and thePCBC is configured to perform the PCBC in preference to the ACC when aperforming condition for the PCBC is satisfied while the ACC is beingperformed and to cancel (stop) the ACC. That is, when the PCBC isperformed while the ACC is being performed, the prior art apparatus isconfigured to cancel the ACC and thereafter not to resume the ACCautomatically after the PCBC is finished (refer to Japanese PatentApplication Laid-Open (kokai) No. 2007-223596.). This is because acollision avoidance function by the PCBC should be given priority over afunction for reducing a driving load of a driver by the ACC. It shouldbe noted that in the Japanese Patent Application Laid-Open (kokai) No.2007-223596, the ACC is referred to as a “traveling state control” andthe PCBC is referred to as a “collision avoidance control”.

SUMMARY

However, according to the prior art apparatus, when the PCBC isperformed during a trailing by the ACC, the ACC is canceled and notresumed after the PCBC is finished. Therefore, a case may arise wherethe driver has a strange or annoying feeling.

More specifically, in a case where the PCBC is performed due to anoccurrence of a situation (hereinafter, also referred to as a “avoidanceoperation necessary situation”) in which a brake operation by the driverduring the trailing by the ACC is considered to be necessary in order toreduce a possibility of a collision, and the driver recognizes thisavoidance operation necessary situation to determine that a decelerationof the own vehicle is necessary, the driver hardly has the strange orannoying feeling even when the ACC is not resumed after the PCBC isfinished.

In contrast, for example, in a case where the PCBC is performed in a“situation where the driver does not consider oneself to be in theavoidance operation necessary situation”, the driver is likely to havethe strange or annoying feeling when the ACC is not resumed after thePCBC is finished. Here, following two cases can be specifically shown asthe case where the PCBC is performed in the aforementioned situation.That is:

A case where the own vehicle approaches the preceding vehicle as aresult of the driver trying to pass (overtake) the preceding vehicle byoperating the steering wheel, and a performing condition for the PCBC issubsequently satisfied when the own vehicle is performing a decelerationcontrol by the ACC by reason of the preceding vehicle having deceleratedin a midst of the own vehicle trailing the preceding vehicle by the ACC.

A case where the own vehicle approaches a pedestrian or a bicycleexisting beside a curved road, and the performing condition for the PCBCis subsequently satisfied when the own vehicle is performing thedeceleration control by the ACC by reason of the preceding vehiclehaving approached the curved road and decelerated in a midst of the ownvehicle trailing the preceding vehicle by the ACC.

In these case, the driver is likely to have the strange or annoyingfeeling since the driver is expecting the ACC to be continued.

In addition, for example, also in a case where the PCBC is performed ina “situation where the driver recognizes (considers) oneself to be inthe avoidance operation necessary situation, however, the driver has anintention to avoid a collision by the steering wheel operation insteadof the brake operation”, the driver is likely to have the strange orannoying feeling when the ACC is not resumed after the PCBC is finished.

The present disclosure is made in order to resolve the problem above.That is, one of objects of the present disclosure is to provide avehicle control apparatus capable of reducing a possibility of causing astrange or annoying feeling to a driver by continuing or resuming an ACCdepending on a situation in a case when a performing condition for aPCBC is satisfied during the trailing by the ACC.

First vehicle control apparatus (hereinafter, also referred to as a“first apparatus”) according to the present disclosure is applied to anown vehicle (100), and comprises:

an electric control unit configured to:

perform, as an adaptive cruise control, a preceding vehicle trailingcontrol which makes said own vehicle (100) trail a preceding vehicle(200) which is a vehicle traveling ahead of said own vehicle (100) bycalculating a target acceleration based on a distance to said precedingvehicle (200) and a relative speed with respect to said precedingvehicle (200);

perform an acceleration control for accelerating said own vehicle (100)and a deceleration control for decelerating said own vehicle (100) sothat an acceleration of said own vehicle (100) coincides with saidtarget acceleration;

calculate a time-to-collision (TTC) to a target object positioned in apredetermined region including a traveling direction of said own vehicle(100) based on a distance to said target object and a relative speed ofsaid target object; and

determine that a performing condition for a first brake control whichautomatically applies a predetermined first braking force to said ownvehicle (100) is satisfied when said time-to-collision (TTC) is lessthan a predetermined first threshold (TTCth1, TTCth2) so as to performsaid first brake control.

The electric control unit is further configured to:

continue performing said adaptive cruise control when said decelerationcontrol is being performed at a point in time when said performingcondition for said first brake control has been determined to besatisfied during a performance of said adaptive cruise control;

stop performing said adaptive cruise control when said decelerationcontrol is not being performed at said point in time; and

not to perform said first brake control when a performance of saidadaptive cruise control is continued in a case where said performingcondition for said first brake control is determined to be satisfiedduring a performance of said adaptive cruise control.

In the first apparatus, when the deceleration control is being performedat the point in time when the performing condition for the first brakecontrol has been determined to be satisfied during a performance of theadaptive cruise control (ACC), the first brake control is not performedbut the performance of the ACC (that is, a control including thepreceding vehicle trailing control as one aspect thereof) is continued.

The performing condition for the first brake control is determined to besatisfied when the time-to-collision to the target object is less thanthe first threshold. The case where the deceleration control is beingperformed by the ACC at the point in time when the performing conditionfor the first brake control has been determined to be satisfied ishighly likely to be a case where the time-to-collision becomes less thanthe first threshold in the “situation where the driver does not consideroneself to be in the avoidance operation necessary situation” or in the“situation where the driver recognizes (considers) oneself to be in theavoidance operation necessary situation, however, the driver has anintention to avoid a collision by the steering wheel operation insteadof the brake operation”. That is, the case above is highly likely to bea case where the driver does not assume the first brake control to beperformed and rather expects the performance of the ACC to be continued.According to the first apparatus, the first brake control is notperformed but the performance of the ACC is continued in such a case.Therefore, an occurrence of a situation where the first brake control isperformed and the ACC is stopped contrary to the driver's expectationcan be suppressed, and a possibility of giving a strange and annoyingfeeling to the driver can be reduced.

In another aspect of the present disclosure,

the electric control unit is configured to:

perform, as said adaptive cruise control, an acceleration overridecontrol which accelerates said own vehicle (100) in response to anaccelerator operation by a driver of said own vehicle (100) when arequired acceleration based on said accelerator operation is greaterthan said target acceleration,

continue performing said adaptive cruise control when said accelerationoverride control is being performed at said point in time when saidperforming condition for said first brake control has been determined tobe satisfied during a performance of said adaptive cruise control; and

stop performing said adaptive cruise control when said accelerationoverride control is not being performed at said point in time.

In the configuration above, when the acceleration override control isbeing performed at the point in time when the performing condition forthe first brake control has been determined to be satisfied during aperformance of the ACC, the first brake control is not performed but theperformance of the ACC (that is, a control including the accelerationoverride control as one aspect thereof) is continued.

The case where the acceleration override control is being performed atthe point in time when the performing condition for the first brakecontrol has been determined to be satisfied is also likely to be a casewhere the time-to-collision becomes less than the first threshold in the“situation where the driver does not consider oneself to be in theavoidance operation necessary situation”. Specifically, this casecorresponds to a case where the own vehicle approaches the precedingvehicle as a result of the driver trying to pass (overtake) thepreceding vehicle by operating the steering wheel while performing theacceleration override control during the trailing of the precedingvehicle by the ACC, and the time-to-collision subsequently becomes lessthan the first threshold. According to the configuration above, in sucha case, the first brake control is not performed but the performance ofthe ACC is continued. Therefore, the occurrence of the situation wherethe first brake control is performed, and the ACC is stopped contrary tothe driver's expectation can be suppressed more, and the possibility ofgiving a strange and annoying feeling to the driver can be more reduced.

In another aspect of the present disclosure,

the electric control unit is configured to:

perform said first brake control when said time-to-collision is lessthan said first threshold and more than or equal to a second thresholdsmaller than said first threshold;

determine that a performing condition for a second brake control whichapplies a second braking force greater than said first braking force tosaid own vehicle is satisfied when said time-to-collision is less thansaid second threshold so as to perform said second brake control; and

stop performing said adaptive cruise control when said second brakecontrol is started during a performance of said adaptive cruise control.

In the configuration above, the performance of the ACC is stopped whenthe performing condition for the second brake control has beendetermined to be satisfied during the performance of the ACC andthereafter the second brake control is started. The second brake controlherein is a control which applies the second braking force greater thanthe first braking force when the own vehicle is approaching the targetobject closer than when the first brake control is performed. Therefore,the second brake control can be said to be a control which is performedwhen there is a higher necessity of an avoidance operation compared tothe first brake control. In general, the driver does not expect the ACCto be continued when there is a high necessity of the avoidanceoperation. Thus, according to the configuration above, it becomespossible to surely ensure a deceleration amount by performing the secondbrake control, maintaining the possibility of giving a strange andannoying feeling to the driver low.

In another aspect of the present disclosure,

the electric control unit is configured to change said second threshold(TTCth3) in a case when a target object, said time-to-collision (TTC)thereof being less than said first threshold (TTCth1), is said precedingvehicle (200) in such a manner that said second threshold (TTCth3)becomes smaller as a lap rate (LR) becomes low, said lap rate (LR) beinga value obtained by dividing a length (L) by which said own vehicle(100) overlaps with said preceding vehicle (200) in a vehicle widthdirection of said own vehicle (100) when assuming that said own vehicle(100) collides with said preceding vehicle (200), by a vehicle width (W)of said own vehicle (100).

In the configuration above, even though the time-to-collision to thepreceding vehicle becomes shorter (that is, even though the own vehicleapproaches the preceding vehicle closer), as the lap rate becomes lower,the first brake control becomes more difficult to be performed and theACC becomes easier to be continued. It is highly likely that as the laprate becomes lower, a distance to the preceding vehicle becomes shorterfor a purpose of the own vehicle passing the preceding vehicle or thedriver of the own vehicle avoiding a collision with the precedingvehicle by the steering wheel operation. Therefore, according to theconfiguration above, a possibility that the first brake control isperformed and the ACC is stopped contrary to the driver's expectationcan be further reduced.

Second vehicle control apparatus (hereinafter, also referred to as a“second apparatus”) according to the present disclosure is applied to anown vehicle (100), and comprises:

an electric control unit configured to:

perform, as an adaptive cruise control, a preceding vehicle trailingcontrol which makes said own vehicle (100) trail a preceding vehicle(200) which is a vehicle traveling ahead of said own vehicle (100) bycalculating a target acceleration based on a distance to said precedingvehicle (200) and a relative speed with respect to said precedingvehicle (200);

perform an acceleration control for accelerating said own vehicle (100)and a deceleration control for decelerating said own vehicle (100) sothat an acceleration of said own vehicle (100) coincides with saidtarget acceleration;

calculate a time-to-collision (TTC) to a target object positioned in apredetermined region including a traveling direction of said own vehicle(100) based on a distance to said target object and a relative speed ofsaid target object; and

determine that a performing condition for a first brake control whichautomatically applies a predetermined first braking force to said ownvehicle (100) is satisfied when said time-to-collision (TTC) is lessthan a predetermined first threshold (TTCth1, TTCth2) so as to performsaid first brake control.

The electric control unit is configured to:

stop performing said adaptive cruise control in a case where said firstbrake control is started during a performance of said adaptive cruisecontrol; and

automatically resume said adaptive cruise control when said first brakecontrol started during a performance of said adaptive cruise control isfinished in a case where said deceleration control is being performed ata point in time when said performing condition for said first brakecontrol has been determined to be satisfied.

In the second apparatus, the performance of the ACC is stopped in a casewhere the performing condition for the first brake control has beendetermined to be satisfied during the performance of the adaptive cruisecontrol (ACC) and thereafter the first brake control is started.Besides, the ACC (that is, a control including the preceding vehicletrailing control as one aspect thereof) is automatically resumed whenthe first brake control started during the performance of the ACC isfinished in a case where the deceleration control by the ACC is beingperformed at a point in time when the performing condition for the firstbrake control has been determined to be satisfied.

The performing condition for the first brake control is determined to besatisfied when the time-to-collision to the target object is less thanthe first threshold. The case where the deceleration control is beingperformed by the ACC at the point in time when the performing conditionfor the first brake control has been determined to be satisfied ishighly likely to be a case where the time-to-collision becomes less thanthe first threshold in the “situation where the driver does not consideroneself to be in the avoidance operation necessary situation” or in the“situation where the driver recognizes (considers) oneself to be in theavoidance operation necessary situation, however, the driver has anintention to avoid a collision by the steering wheel operation insteadof the brake operation”. That is, it is highly likely that the driverdoes not expect the performance of the ACC to continue to be stoppedalso after the first brake control is finished. According to the secondapparatus, in such a case, the ACC is automatically resumed after thefirst brake control is finished. Therefore, an occurrence of a situationwhere the ACC continues to be stopped after the first brake control isstopped contrary to the driver's expectation can be suppressed, and apossibility of giving a strange and annoying feeling to the driver canbe reduced.

In another aspect of the present disclosure,

the electric control unit is configured to:

perform, as said adaptive cruise control, an acceleration overridecontrol which accelerates said own vehicle (100) in response to anaccelerator operation by a driver of said own vehicle (100) when arequired acceleration based on said accelerator operation is greaterthan said target acceleration; and

automatically resume said adaptive cruise control when said first brakecontrol started during a performance of said adaptive cruise control isfinished in a case where said acceleration override control is beingperformed at said point in time when said performing condition for saidfirst brake control has been determined to be satisfied.

In the configuration above, the ACC (that is, a control including theacceleration override control as one aspect thereof) is resumedautomatically when the first brake control started during theperformance of the ACC is finished in a case where the accelerationoverride control is being performed at the point in time when theperforming condition for the first brake control has been determined tobe satisfied.

The case where the acceleration override control is being performed atthe point in time when the performing condition for the first brakecontrol has been determined to be satisfied is also likely to be a casewhere the time-to-collision becomes less than the first threshold in the“situation where the driver does not consider oneself to be in theavoidance operation necessary situation”. Specifically, this casecorresponds to a case where the own vehicle approaches the precedingvehicle as a result of the driver trying to pass (overtake) thepreceding vehicle by operating the steering wheel while the accelerationoverride control being performed during the trailing of the precedingvehicle by the ACC, and the time-to-collision subsequently becomes lessthan the first threshold. According to the configuration above, in sucha case, the ACC is automatically resumed after the first brake controlis finished. Therefore, the occurrence of the situation where the ACCcontinues to be stopped after the first brake control is finishedcontrary to the driver's expectation can be suppressed more, and thepossibility of giving a strange and annoying feeling to the driver canbe reduced more.

In another aspect of the present disclosure,

the electric control unit is configured to:

perform said first brake control when said time-to-collision (TTC) isless than said first threshold (TTCth1, TTCth2) and more than or equalto a second threshold (TTCth3, TTCth4) smaller than said first threshold(TTCth1, TTCth2);

determine that a performing condition for a second brake control whichapplies a second braking force greater than said first braking force tosaid own vehicle (100) is satisfied when said time-to-collision (TTC) isless than said second threshold (TTCth3, TTCth4) so as to perform saidsecond brake control;

stop performing said adaptive cruise control when said second brakecontrol is started during a performance of said adaptive cruise control;and

continue stopping a performance of said adaptive cruise control whensaid second brake control started during a performance of said adaptivecruise control is finished.

In the configuration above, the performance of the ACC is stopped whenthe performing condition for the second brake control has beendetermined to be satisfied during the performance of the ACC andthereafter the second brake control is started. Besides, after thesecond brake control is finished, the performance of the ACC continuesto be stopped (is not resumed). The second brake control herein is acontrol which applies the second braking force greater than the firstbraking force when the own vehicle is approaching the target objectcloser than when the first brake control is performed. Therefore, thesecond brake control can be said to be a control which is performed whenthere is a higher necessity of an avoidance operation compared to thefirst brake control. In general, the driver does not expect the ACC tobe resumed when there is a high necessity of the avoidance operation.Thus, according to the configuration above, it becomes possible tosurely ensure a deceleration amount by performing the second brakecontrol, maintaining the possibility of giving a strange and annoyingfeeling to the driver low.

In another aspect of the present disclosure,

the electric control unit is configured to change said second threshold(TTCth3) in a case when a target object, said time-to-collision (TTC)thereof being less than said first threshold (TTCth1), is said precedingvehicle (200) in such a manner that said second threshold (TTCth3)becomes smaller as a lap rate (LR) becomes low, said lap rate (LR) beinga value obtained by dividing a length (L) by which said own vehicle(100) overlaps with said preceding vehicle (200) in a vehicle widthdirection of said own vehicle (100) when assuming that said own vehicle(100) collides with said preceding vehicle (200), by a vehicle width ofsaid own vehicle (100).

In the configuration above, even though the time-to-collision to thepreceding vehicle becomes shorter (that is, even though the own vehicleapproaches the preceding vehicle closer), as the lap rate becomes lower,the ACC becomes easier to be resumed after the first brake control isfinished. It is highly likely that as the lap rate becomes lower, adistance to the preceding vehicle becomes shorter for a purpose of theown vehicle passing the preceding vehicle or the driver of the ownvehicle avoiding a collision with the preceding vehicle by the steeringwheel operation. Therefore, according to the configuration above, apossibility that the ACC continues to be stopped after the first brakecontrol is finished contrary to the driver's expectation can be furtherreduced.

In the above description, references used in the following descriptionsregarding embodiments are added with parentheses to the elements of thepresent disclosure, in order to assist in understanding the presentdisclosure. However, those references should not be used to limit thescope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is diagram showing a vehicle control apparatus (hereinafter,referred to as a “first embodiment apparatus”) according to a firstembodiment of the present disclosure and a vehicle to which the firstembodiment apparatus is applied.

FIG. 2 is a diagram for describing a lap rate.

FIG. 3 is a graph showing a relationship between a brake avoidance limittime, a steering avoidance limit time and the lap rate.

FIG. 4A is a diagram showing a situation where an own vehicle changes atraffic lane by a steering wheel operation in order to pass a precedingvehicle during a deceleration control by an ACC.

FIG. 4B is a diagram showing a situation where the own vehicle is tryingto avoid a collision with the preceding vehicle by the steering wheeloperation during the deceleration control by the ACC.

FIG. 4C is a diagram showing a situation where there exists a bicycle ora pedestrian in a predetermined region (a detection region of a targetobject subject to a PCBC) including a traveling direction of the ownvehicle during the deceleration control by the ACC on a curved road.

FIG. 5 is a flowchart showing a routine performed by CPU (hereinafter,referred to as “CPU of the first embodiment apparatus”) of a vehiclecontrol ECU of the first embodiment apparatus.

FIG. 6 is a flowchart showing a routine performed by the CPU of thefirst embodiment apparatus.

FIG. 7 is a flowchart showing a routine performed by the CPU of thefirst embodiment apparatus.

FIG. 8 is a flowchart showing a routine performed by the CPU of thefirst embodiment apparatus.

FIG. 9 is a flowchart showing a routine performed by the CPU of thefirst embodiment apparatus.

FIG. 10 is a flowchart showing a routine performed by CPU of a secondembodiment apparatus.

FIG. 11 is a flowchart showing a routine performed by CPU of a thirdembodiment apparatus.

FIG. 12 is a flowchart showing a routine performed by CPU of a fourthembodiment apparatus.

DESCRIPTION OF THE EMBODIMENT First Embodiment

A vehicle control apparatus (a first embodiment apparatus) according toa first embodiment of the present disclosure will be described below,referring to FIG. 1 through FIG. 9. The first embodiment apparatus isapplied to a vehicle 100 shown in FIG. 1. The vehicle 100 is anautomobile, a power source thereof being an engine (illustrationomitted). As shown in FIG. 1, the first embodiment apparatus comprises avehicle control ECU 10 (hereinafter, also referred to as “ECU 10”).

ECU is an abbreviation of Electric Control Unit, and the ECU 10 is anelectronic control circuit having a microcomputer including CPU, ROM,RAM, an interface I/F, and the like as main components. The CPU isconfigured to realize/perform various functions mentioned later byexecuting instructions (i.e., programs or routines) stored in a memory(the ROM).

To the ECU 10, a vehicle speed sensor 11, an accelerator pedal operationamount sensor 12, a brake pedal operation amount sensor 13, a yaw ratesensor 14, a radar sensor 15, a camera 16, an adaptive cruise controlswitch (hereinafter, also referred to as an “ACC switch”) 17, a vehiclespeed-inter-vehicular distance setting switch 18, a throttle actuator 19and a brake actuator 20 are connected. It should be noted that althoughthe vehicle 100 comprises a plurality of sensors for detecting a drivingstate of the vehicle 100 other than the sensors mentioned above, onlysensors related to a configuration of the vehicle control apparatusdisclosed in the present specification are described in the presentembodiment.

The vehicle speed sensor 11 is configured to detect a speed of thevehicle 100 (a vehicle speed) and output a signal representing the speedto the ECU 10.

The accelerator pedal operation amount sensor 12 is configured to detectan operation amount of an accelerator pedal (illustration omitted), andoutput to the ECU 10 a signal representing the operation amount(hereinafter, referred to as an “accelerator pedal operation amount”).

The brake pedal operation amount sensor 13 is configured to detect anoperation amount of a brake pedal (illustration omitted), and output tothe ECU 10 a signal representing the operation amount (hereinafter,referred to as a “brake pedal operation amount”).

The yaw rate sensor 14 is configured to detect an angular speed (a yawrate) of the vehicle 100, and output a signal representing the yaw rateto the ECU 10.

The radar sensor 15 is configured to transmit a radio wave toward afront direction (that is, a diagonally front left direction, a forwarddirection and a diagonally front right direction) of the vehicle 100.When there exist a movable object and a building (described later) in aregion which the radio wave (hereinafter, referred to as a “transmittedwave”) reaches, the transmitted wave is reflected by the object and thebuilding. The radar sensor 15 is configured to receive the reflectedtransmitted wave (hereinafter, referred to as a “reflected wave”). Theradar sensor 15 is configured to output to the ECU 10 a signalrepresenting the transmitted wave and a signal representing thereflected wave. It should be noted that specifically, the movable objectmeans an object such as an other vehicle, a pedestrian, a bicycle andthe like, and the building means a guard rail, a wall provided along aside of an expressway, a median strip and the like.

The camera 16 is configured to photograph a front of the vehicle 100,and output a signal representing an image data photographed to the ECU10.

The ACC switch 17 is provided near a driver's seat, and is operated by adriver. When the ACC switch 17 is turned on, a signal for switching atraveling mode of the vehicle 100 to a “traveling mode at a constant,speed” or a “trailing mode” (both will be described later) is output tothe ECU 10. At this time, the ACC switch 17 changes from an off state toan on state, and during the ACC switch 17 being on, outputs to the ECU10 a signal representing that the ACC switch 17 is in the on state. Whenthe ACC switch 17 is turned off, a signal for switching the travelingmode of the vehicle 100 to a normal traveling mode is output to the ECU10. At this time, the ACC switch 17 changes from the on state to the offstate, and during the ACC switch 17 being off, outputs to the ECU 10 asignal representing that the ACC switch 17 is in the off state. Itshould be noted that the traveling mode at a constant speed is atraveling mode selected by the ACC switch 17 being turned on in a casewhen no preceding vehicle (that is, a vehicle existing ahead of thevehicle 100 on a same traffic lane as the vehicle 100) exists. Thetrailing mode is a traveling mode selected by the ACC switch 17 being onin a case when there exists a preceding vehicle.

The vehicle speed-inter-vehicular distance setting switch 18 is providednear the driver's seat, and is operated by the driver. When a vehiclespeed and an inter-vehicular distance are set by the driver adjustingthe vehicle speed-inter-vehicular distance setting switch 18, signalsrepresenting these vehicle speed and inter-vehicular distance are outputto the ECU 10 as signals representing a set vehicle speed and a setinter-vehicular distance, respectively. The set vehicle speed herein isa vehicle speed at which the vehicle 100 maintains when the travelingmode of the vehicle 100 is the traveling mode at a constant speed. Theset inter-vehicular distance herein is an inter-vehicular distance withthe preceding vehicle which the vehicle 100 maintains, traveling at avehicle speed less than or equal to the set vehicle speed when thetraveling mode of the vehicle 100 is the trailing mode. It should benoted that a configuration where a vehicle-to-vehicle time is setinstead of the inter-vehicular distance may be adopted. In this case,the set inter-vehicular distance can be calculated by multiplying theset vehicle-to-vehicle time by the vehicle speed.

The throttle actuator 19 is an apparatus for changing a throttle valveopening by driving a throttle valve provided at an engine intake duct ofthe vehicle 100. The ECU 10 operates the throttle actuator 19 based onthe accelerator pedal operation amount detected by the accelerator pedaloperation amount sensor 12 and a driving state amount (for example, anengine rotating speed) detected by an other engine state amount sensor(illustration omitted) of the vehicle 100. When the ECU 10 operates thethrottle actuator 19, an acceleration of the vehicle 100 changes since agenerated torque and an output of the engine changes.

The brake actuator 20 is provided in a hydraulic circuit between amaster cylinder to compress operating fluid with a depression force ofthe brake pedal and a friction brake mechanism provided at each of frontand rear wheels of the vehicle 100. Each of the friction brake mechanismoperates a wheel cylinder with operating fluid supplied from the brakeactuator 20, and thereby presses a corresponding brake pad onto acorresponding brake disc provided at each of the front and rear wheelsto generate a hydraulic braking force. The brake actuator 20 is a knownactuator for adjusting a hydraulic pressure supplied to the wheelcylinder, and supplies to the wheel cylinder a hydraulic pressure inresponse to an instruction from the ECU 10 to generate a braking forcefor each of the wheels.

The ECU 10 operates the brake actuator 20 based on the brake pedaloperation amount detected by the brake pedal operation amount sensor 13and a driving state amount detected by an other driving state amountsensor (illustration omitted) of the vehicle 100. When the ECU 10operates the brake actuator 20, a deceleration of the vehicle 100changes since a braking force is applied to each of the front and rearwheels.

<Summary of Operation of the First Embodiment Apparatus>

Next, a summary of operation of the first embodiment apparatus will bedescribed. The first embodiment apparatus adopts a pre-crash safetysystem (PCS) and determines whether or not to perform a pre-crash brakecontrol (hereinafter, also referred to as a “PCBC”) every time apredetermined calculation interval elapses. The PCBC of the firstembodiment apparatus is a control to apply a predetermined braking forceto the vehicle 100 in a case when there exists a target object, atime-to-collision thereof being less than a predetermined time thresholdin a predetermined region including a traveling direction of the vehicle100.

There are two types in the PCBC; one is a pre brake control whichapplies a regular braking force and an other is a light pre brakecontrol which applies a light braking force lighter than the regularbraking force. Hereinafter, the pre brake control is referred to as a“PBC” and the light pre brake control is referred to as a “LPBC”. ThePBC is performed when a collision risk is relatively high and the LPBCis performed when the collision risk is relatively low. It should benoted that the regular braking force and the light braking forcecorrespond to one example of a “second braking force” and a “firstbraking force”, respectively. Besides, the PBC and the LPBC correspondto one example of a “second brake control” and a “first brake control”,respectively.

In addition, the first embodiment apparatus determines whether or notthe ACC switch 17 is in the on state every time the predeterminedcalculation interval elapses, and when the ACC switch 17 is in the onstate, performs an adaptive cruise control (hereinafter, also referredto as an “ACC”). There are two types in the ACC, one is a control at thetraveling mode at a constant speed, and an other is a control at thetrailing mode. The present disclosure disclosed in the presentspecification is based on a premise that the first embodiment apparatusperforms the ACC at the trailing mode (that is, the vehicle 100 trailsthe preceding vehicle), and therefore hereinafter, a case where thefirst embodiment apparatus performs the ACC at the trailing mode will bemainly described. The ACC at the trailing mode is a control whichperforms an acceleration control or a deceleration control of thevehicle 100 in such a manner that the vehicle 100 trails the precedingvehicle at a vehicle speed less than or equal to the set vehicle speed,maintaining an inter-vehicular distance with the preceding vehicle asthe set inter-vehicular distance. It should be noted that the ACC at thetrailing mode corresponds to one example of a “preceding vehicletrailing control”.

The first embodiment apparatus determines whether “to continue the ACCwithout performing the PCBC” or “to perform the PCBC and stop the ACC”when having determined that the performing condition for the PCBC issatisfied during a performance of the ACC at the trailing mode (ACCdetermination). That is, the first embodiment apparatus does not alwaysperform the PCBC even when having determined that the performingcondition for the PCBC is satisfied. Now, if the ACC is resumedautomatically after the performance of the PCBC, there is a possibilitythat the driver overestimates a performance of the first embodimentapparatus and does riot intervene in a brake control after theperformance of the PCBC. Therefore, in a situation where the collisionrisk is expected to be relatively high, it is desired to prompt thedriver to surely intervene in the brake control by stopping theperformance of the ACC after the performance of the PCBC. Thus, when atype of the PCBC is the PBC (that is, a control performed when thecollision risk is relatively high), the first embodiment apparatusdetermines that the PBC alone is insufficient, and performs the PBC andstops the performance of the ACC.

On the other hand, in a configuration where the PCBC is performed andthe performance of the ACC is always stopped, if the performingcondition for the PCBC happens to be satisfied contrary to a driver'sintention, the PCBC will be performed and the ACC will be stoppedcontrary to a driver's expectation, which is not desirable.

FIG. 4A through FIG. 4C show examples of situations where a possibilitythat the performing condition for the PCBC happens to be satisfiedcontrary to the driver's intention is high. In FIG. 4A and FIG. 4B, thevehicle 100 is performing the deceleration control by the ACC since apreceding vehicle 200 decelerated in a midst of the vehicle 100 trailingthe preceding vehicle 200. In FIG. 4A, when the driver operates thesteering wheel for a purpose of passing the preceding vehicle 200 andchanges a traffic lane along a path shown by an arrow of FIG. 4A, it ishighly likely that the performing condition for the PCBC is satisfiedsince the vehicle 100 temporarily approaches the preceding vehicle 200.In FIG. 4B, when the driver operates the steering wheel in order to tryto avoid a collision by traveling along a path shown by an arrow of FIG.4B, it is highly likely that the performing condition for the PCBC issatisfied since the vehicle 100 temporarily approaches the precedingvehicle 200. On the other hand, in FIG. 4C, the vehicle 100 isperforming the deceleration control by the ACC since the precedingvehicle 200 approached a curved road and thus decelerated in a midst ofthe vehicle 100 trailing the preceding vehicle 200. As shown in FIG. 4C,a bicycle 300 existing beside the curved road is included in apredetermined region S (a detection region of a target object subject tothe PCBC) including a traveling direction of the vehicle 100 (refer toan arrow in FIG. 4C). It is highly likely that the performing conditionfor the PCBC is satisfied when the vehicle 100 approaches the bicycle300 due to a road shape.

As is obvious from a description above, in a “case where the performingcondition for the PCBC happens to be satisfied contrary to the driver'sintention”, the collision risk is expected to be relatively low.Therefore, when a type of the PCBC is the LPBC (that is, a controlperformed when the collision risk is relatively low), the firstembodiment apparatus continues the ACC without performing the LPBC ifthe deceleration control by the ACC is being performed at a point intime when the performing condition for the LPBC has been determined tobe satisfied, whereas the first embodiment apparatus performs the LPBCand stops the ACC if the deceleration control by the ACC is not beingperformed (that is, the acceleration control by the ACC or theacceleration override control is being performed) at the point in timewhen the performing condition for the LPBC has been determined to besatisfied. That is, assuming that the performing condition for the LPBChas been determined to be satisfied in the examples of FIG. 4A throughFIG. 4C, the deceleration control by the ACC is being performed at apoint in time when the determination has been made, and therefore theLPBC will not be performed but the ACC will be continued. Therefore, itcan be prevented that the LPBC is performed and the performance of theACC is stopped contrary to the driver's expectation. As is clear fromthe description above, an action that “the deceleration control by theACC is being performed at the point in time when the performingcondition for the PCBC has been determined to be satisfied” is includedin one of conditions for determining whether to continue the ACC or tostop the ACC. This is because if the ACC is the acceleration control(including an acceleration of zero) or the acceleration overridecontrol, a deceleration amount based on the ACC cannot be ensured unlikea case where the ACC is the deceleration control, which may cause thedeceleration amount based on the LPBC alone to be insufficient even in asituation with a low collision risk and therefore it is desirable toprompt the driver to intervene in the brake control.

Hereinafter, a description about the PCBC, the ACC and an ACCdetermination process will be made in detail based on the summary statedabove. It should be noted that hereinafter, a period between when anon-illustrated engine switch (an ignition key switch) of the vehicle100 is turned on and when this engine switch is turned off will be alsoreferred to as an “engine on period”.

<Detail of Operation of the First Embodiment Apparatus> A. PCBC[Acquisition of Own Vehicle Information]

First, a description about the PCBC will be made. The ECU 10 acquiresinformation showing the vehicle speed, the accelerator pedal operationamount, the brake pedal operation amount, the yaw rate, the state of theACC switch 17 and the state of the vehicle speed-inter-vehiculardistance setting switch 18 (that is, the driving state of the vehicle100) as own vehicle information based on the signals received from thesensors 11 to 14 and the switches 17 and 18 every time the predeterminedcalculation interval elapses during the engine on period. Besides, theECU 10 calculates the traveling direction of the vehicle 100 based onthe vehicle speed and the yaw rate.

[Acquisition of Target Object Information]

The ECU 10 determines whether or not there exist any movable objects(hereinafter, simply referred to as an “object”) around the vehicle 100from a signal received from the radar sensor 15 and an image data basedon a signal received from the camera 16 every time the predeterminedcalculation interval elapses during the engine on period. When the ECU10 has determined that there exists an object, the ECU 10 calculates adistance from the vehicle 100 to the object and an azimuth with respectto the vehicle 100. In addition, the ECU 10 calculates the relativespeed of the object with respect to the vehicle 100 based on a speed ofthe object and the speed of the vehicle 100.

The ECU 10 fuses the signal of the object received from the radar sensor15 and the image data of that object obtained from the camera 16 togenerate a fusion object. Specifically, the ECU 10 identifies alongitudinal position of the fusion object using the distance to theobject and the relative speed thereof calculated based on the signalreceived from the radar sensor 15, and identifies a lateral position ofthe fusion object using a lateral width and a lateral position of theobject calculated based on the image data obtained from the camera 16.The ECU 10 stores in the memory (ROM) the patterned data of objects suchas a vehicle, a pedestrian, a bicycle and the like in advance. The ECU10 performs a pattern matching for the image data obtained from thecamera 16 using this patterned data and thereby recognizes to whichobject pattern among a vehicle, a pedestrian or a bicycle an objectshown by this image data corresponds.

Hereinafter, a fusion object which satisfies following conditions willbe defined as a “target object”. The conditions are as follows:

-   A fusion object is either one of a vehicle, a pedestrian or a    bicycle which is positioned in the predetermined region (a region    defined by an angle range) including the traveling direction of the    vehicle 100.-   A relative speed of a fusion object in a vehicle width direction (a    direction perpendicular to the traveling direction of the vehicle    100) is in a predetermined relative speed range including zero.

That is, for example, even though a fusion object recognized as abicycle by the pattern matching is positioned in the predeterminedregion, this fusion object does not correspond to a target object if arelative speed thereof in the vehicle width direction is out of thepredetermined relative speed range. In addition, a fusion object withspeed thereof being zero is also included as a target object. The ECU 10acquires, as target object information, information showing the distancefrom the vehicle 100 to the target object, the azimuth of the targetobject with respect to the vehicle 100, the relative speed of the targetobject with respect to the vehicle 100 and to which object pattern thetarget object corresponds among a vehicle, a pedestrian and a bicycle.It should be noted that although a scanning region of the radar sensor15 and a photographing region of the camera 16 are set as wider regionsthan the predetermined region mentioned above, a configuration is notlimited thereto. The scanning region and the photographing region may besubstantially same as the predetermined region mentioned above.

[Calculation of a Time-to-Collision]

The ECU 10 calculates a time-to-collision (hereinafter, also referred toas a “TTC”) to each of the fusion objects detected as target objectsevery time the predetermined calculation interval elapses during theengine on period. The TTC to each target object can be calculated bydividing a distance to each target object by a relative speed of thevehicle 100 with respect to each target object. When there are pluralityof target objects, the ECU 10 compares the TIC to each target object toselect among them one target object with a minimum TTC, and determineswhether or not to determine the PCBC (described later) against thetarget object selected.

The ECU 10 determines whether or not the performing condition forperforming the PCBC against the selected target object is satisfiedevery time the predetermined calculation interval elapses during theengine on period. When the ECU 10 has determined that the performingcondition is satisfied, the ECU 10 determines whether to continue theACC without performing the PCBC or whether to perform the PCBC and stopthe ACC. As mentioned earlier, there are two types in the PCBC; one isthe PBC and the other is the LPBC. The performing conditions for thesetwo controls are different, depending on whether a target object is another vehicle (typically, a preceding vehicle) or a pedestrian/abicycle. Therefore, hereinafter, a case where the target object is theother vehicle and a case where the target object is the pedestrian orthe bicycle will be separately described regarding the PBC and the LPBC.

[PBC in a Case When the Target Object is an Other Vehicle]

First, a description about the PBC in a case when the target object isthe other vehicle will be made. There are two methods in avoiding acollision with the other vehicle by a driving operation by the driveroneself; one is a collision avoidance by a brake operation by the driver(hereinafter, also referred to as a “brake avoidance”) and an other is acollision avoidance by a steering wheel operation by the driver(hereinafter, also referred to as a “steering avoidance”). It isdesirable that the PBC is performed when only the brake operation or thesteering operation by the driver may be difficult to avoid a collision(that is, when the collision risk is relatively high).

FIG. 3 is a graph showing a relationship between a brake avoidance limittime T_(B), a steering avoidance limit time T_(S) and a lap rate LR, andthis graph is stored in the memory (ROM). The brake avoidance limit timeT_(B) herein is a limit time for the driver to be able to avoid acollision with the other vehicle by the brake operation. The steeringavoidance limit time T_(S) is a limit time for the driver to be able toavoid a collision with the other driver by the steering wheel operation.The lap rate LR is, as shown in FIG. 2, an index showing an overlappingdegree of the vehicle 100 with the other vehicle 200 in the vehiclewidth direction. The lap rate LR can be calculated by dividing a lengthL by which the vehicle 100 overlaps with the other vehicle 200 in thevehicle width direction of the vehicle 100 by a vehicle width W of thevehicle 100.

In FIG. 3, a vertical axis represents the TTC and a horizontal axisrepresents the lap rate LR. Values of the vertical axis become smallerdownwardly, and values of the lateral axis become smaller outwardly froma center. A right side part of the lateral axis represents the lap rateLR of when the vehicle 100 is positioned on a right side with respect tothe other vehicle, and a left side part of the lateral axis representsthe lap rate LR of when the vehicle 100 is positioned on a left sidewith respect to the other vehicle.

As shown in FIG. 3, although the brake avoidance limit time T_(B) isconstant regardless of the lap rate LR, the steering avoidance limittime T_(S) changes with the lap rate LR. A value of the steeringavoidance limit time T_(S) is the largest when the lap rate LR is 1 andbecomes smaller as the lap rate LR becomes lower. When the lap rate LRsatisfies LR≥LR2 (Hereinafter, the lap rate LR which satisfies thisrelationship is also referred to as a “high lap”), a time necessary toavoid a collision by the brake operation can be suppressed to a timeless than or equal to a time necessary to avoid the collision by thesteering wheel operation since a relationship of the brake avoidancelimit time T_(B)≤the steering avoidance limit time T_(S) is satisfied.On the other hand, when the lap rate LR satisfies LR1≤LR<LR2(Hereinafter, the lap rate LR which satisfies this relationship is alsoreferred to as a “low lap”.), a time necessary to avoid a collision bythe steering wheel operation can be suppressed to a time less than atime necessary to avoid the collision by the brake operation since arelationship of the steering avoidance limit time T_(S)<the brakeavoidance limit time T_(B) is satisfied.

On the other hand, this can be rephrased as follows.

-   It is highly likely that only the brake operation by the driver is    insufficient to avoid a collision with the other vehicle when the    TTC is less than the brake avoidance limit time T_(B) in a case of    the high lap.-   It is highly likely that only the steering wheel operation by the    driver is insufficient to avoid a collision with the other vehicle    when the TTC is less than the steering avoidance limit time T_(S) in    a case of the low lap.

That is, the collision risk is relatively high in the above two cases.

Therefore, when the TTC is less than the brake avoidance limit timeT_(B) in a case of the high lap and when the TTC is less than thesteering avoidance limit time T_(S) in a case of the low lap (that is,when values of the lap rate LR and the TTC are both positioned within aregion surrounded by a thick line and the horizontal axis in FIG. 3),the ECU 10 determines that the performing condition for the PBC whichapplies the regular braking force is satisfied to perform the PBC. Itshould be noted that the brake avoidance limit time T_(B) corresponds toone example of a “first threshold”. Hereinafter, the brake avoidancelimit time T_(B) is also referred to as a “first time threshold TTCth1”.

[LPBC in a Case When the Target Object is an Other Vehicle]

Next, a description about the LPBC in a case when the target object isthe other vehicle will be made. In a case of the low lap, when the TTCis more than or equal to the steering avoidance limit time T_(S) andless than the brake avoidance limit time T_(B), the collision risk isrelatively low since the steering avoidance is possible although thereis still some collision possibility because the brake avoidance isdifficult. Therefore, when the TTC is more than or equal to the steeringavoidance limit time T_(S) and less than the brake avoidance limit timeT_(B) in a case of the low lap (that is, when values of the lap rate LRand the TTC are both positioned within a region surrounded by a two-dotchain line, the thick line and a line parallel with the vertical axis,passing through a value of LR1 in FIG. 3), the ECU 10 determines thatthe performing condition for the LPBC which applies the light brakingforce is satisfied to perform the LPBC. That is, the ECU 10 performs twostages of the PCBC in a case of the low lap.

However, even though the LPBC is a control which only applies the lightbraking force, if the LPBC is performed when the driver has an intentionto avoid a collision by the steering wheel operation, the LPBC mayinterfere with the driving operation by the driver, causing a strange orannoying feeling to the driver. In addition, when the vehicle 100changes a traffic lane for a purpose of passing the other vehicle, thevehicle 100 may deviate in the vehicle width direction with respect tothe other vehicle, temporarily approaching the other vehicle, and as aresult, the lap rate LR may become low (that is, the low lap), and theTTC may become more than or equal to the steering avoidance limit timeT_(S) and less than the brake avoidance limit time T_(B). In this casealso, if the LPBC is performed, this control may be regarded as anunnecessary control, causing a strange or annoying feeling to the driversince the driver does not consider oneself to be in a situation where acollision avoidance with the other vehicle is necessary.

The situation as described above (that is, the situation where thedriver does not consider oneself to be in a situation where a collisionavoidance with the other vehicle is necessary) is likely to occur whenfollowing two conditions are satisfied.

-   (Condition 1) The performing condition for the LPBC is determined to    be satisfied during a performance of the ACC.-   (Condition 2) The deceleration control by the ACC is being performed    at a point in time when the performing condition for the LPBC has    been determined to be satisfied.

Therefore, the ECU 10 does not always perform the LPBC when havingdetermined that the performing condition for the LPBC is satisfied, butdoes not perform the LPBC when the above two conditions 1 and 2 aresatisfied. According to this configuration, a possibility that the LPBCis regarded as an unnecessary control by the driver can be lowered.Besides, in a case where it turned out that the driver was actually inthe avoidance operation necessary situation even when the above twoconditions were satisfied, a deceleration amount based on thedeceleration control by the ACC can be ensured. Further, when at leastone of the above two conditions are not satisfied, a deceleration amountbased on the LPBC can be ensured.

It should be noted that the steering avoidance limit time T_(S) in acase of the low lap corresponds to one example of a “second threshold”.Hereinafter, LR1 and LR2 are also referred to as a “first lap ratethreshold LRth1” and a “second lap rate threshold LRth2”, respectively,and the steering avoidance limit time T_(S) is also referred to as a“third time threshold TTCth3”.

[PBC and LPBC in a Case When the Target Object is a Pedestrian or aBicycle]

Subsequently, a description about the PBC and the LPBC in a case whenthe target object is the pedestrian or the bicycle will be made. Whenthe target object is the pedestrian or the bicycle, the ECU 10 performstwo stages of the PCBC. That is, when the TTC is less than a “timethreshold of the PBC for a pedestrian/bicycle”, the ECU 10 determinesthat the performing condition for the PBC is satisfied to perform thePBC, and when the TTC is more than or equal to the “time threshold ofthe PBC for a pedestrian/bicycle” and less than a “time threshold of theLPBC for a pedestrian/bicycle”, the ECU 10 determines that theperforming condition for the LPBC is satisfied to perform the LPBC.However, the ECU 10, as with the case when the target object is theother vehicle, does not always perform the LPBC when having determinedthat the performing condition for the LPBC is satisfied, but does notperform the LPBC when the above two conditions 1 and 2 are satisfied.

The “time threshold of the LPBC for a pedestrian/bicycle” and the “timethreshold of the PBC for a pedestrian/bicycle” have both constantvalues, and the former time threshold is set to be a slightly largervalue than the first time threshold TTCth1. It should be noted that the“time threshold of the LPBC for a pedestrian/bicycle” and the “timethreshold of the PBC for a pedestrian/bicycle” correspond to one exampleof a “first threshold” and a “second threshold”, respectively.Hereinafter, the “time threshold of the LPBC for a pedestrian/bicycle”and the “time threshold of the PBC for a pedestrian/bicycle” arereferred to as a “second time threshold TTCth2” and a “fourth timethreshold TTCth4”, respectively,

[Setting of a PCBC Flag]

As is obvious from the description above, the ECU 10 determines that theperforming condition for the PCBC is satisfied when the TTC is less thanthe first time threshold TTCth1 in a case where the target object is another vehicle, and when the TTC is less than the second time thresholdTTCth2 in a case where the target object is a pedestrian or a bicycle.On the other hand, the ECU 10 determines that the performing conditionfor the PCBC is not satisfied when the TTC is more than or equal to thefirst time threshold TTCth1 in a case where the target object is another vehicle, and when the TTC is more than or equal to the second timethreshold TTCth2 in a case where the target object is a pedestrian or abicycle.

The information indicating whether or not the performing condition forthe PCBC is satisfied is used when determining whether or not to performthe ACC determination (described later). Therefore, a PCBC flag which isa flag indicating this information is set in the first embodimentapparatus. The ECU 10 sets a value of the PCBC flag to 1 when havingdetermined that the performing condition for the PCBC is satisfied, andsets the value of the PCBC flag to 0 when having determined that theperforming condition for the PCBC is not satisfied. The ECU 10 uses thevalue of the PCBC flag when determining whether or not to perform theACC determination.

[Setting of a LPBC Flag]

The ECU 10 determines, under a situation where the performing conditionfor the PCBC is satisfied, that the performing condition for the LPBC issatisfied when “the TTC is more than or equal to the third timethreshold TTCth3 in a case of the low lap” in a case where the targetobject is an other vehicle, and when “the TTC is more than or equal tothe fourth time threshold TTCth4” in a case where the target object is apedestrian or a bicycle. On the other hand, the ECU 10 determines thatthe performing condition for the LPBC is not satisfied when theperforming condition for the PCBC is not satisfied, or when theperforming condition for the PBC (described later) is satisfied.

The ACC determination uses the information indicating whether or not theperforming condition for the LPBC is satisfied. Therefore, an LPBC flagwhich is a flag indicating this information is set in the firstembodiment apparatus. The ECU 10 sets a value of the LPBC flag to 1 whenhaving determined that the performing condition for the LPBC issatisfied, and sets the value of the LPBC flag to 0 when havingdetermined that the performing condition for the LPBC is not satisfied.The ECU 10 uses the value of the LPBC flag in the ACC determination.

[Setting of a PBC Flag]

The ECU 10 determines, under the situation where the performingcondition for the PCBC is satisfied, that the performing condition forthe PBC is satisfied to perform the PBC when “the TTC is less than thethird time threshold TTCth3 in a case of the low lap, or in a case ofthe high lap” in a case where the target object is an other vehicle, andwhen “the TTC is less than the fourth time threshold TTCth4” in a casewhere the target object is a pedestrian or a bicycle. On the other hand,the ECU 10 determines that the performing condition for the PBC is notsatisfied to not perform the PBC when the performing condition for thePCBC is not satisfied, or when the aforementioned performing conditionfor the LPBC is satisfied.

A PBC flag which is a flag indicating whether or not the PCBC is the PBCis set in the first embodiment apparatus. The ECU 10 sets a value of thePBC flag to 1 when having determined that the performing condition forthe PBC is satisfied, and sets the value of the PBC flag to 0 whenhaving determined that the performing condition for the PBC is notsatisfied. That is, the value of the PBC flag is set to 0 when the valueof the LPBC flag is set to 1 under a situation where the value of thePCBC flag has been set to 1, and the value of the LPBC flag is set to 0when the value of the PBC flag is set to 1 under the aforementionedsituation.

B. ACC [State of the ACC Switch]

Next, a description about the ACC will be made. The ECU 10 determineswhether or not the information indicating the state of the ACC switch 17which is obtained as the own vehicle information shows the on stateevery time the predetermined calculation interval elapses during theengine on period. When the information shows the on state, the ECU 10performs the ACC.

[Acquisition of Preceding Vehicle Information]

The ECU 10 determines whether or not there exists a preceding vehicleamong fusion objects detected as target objects every time thepredetermined calculation interval elapses during the engine on period.Specifically, the ECU 10 identifies a road shape based on a signal of abuilding received from the radar sensor 15 and an image data of thatbuilding obtained from the camera 16. Based on the road shapeidentified, the ECU 10 determines whether or not there exists an othervehicle ahead of the vehicle 100 on a traffic lane on which the vehicle100 is traveling. The ECU 10 determines that there exists a precedingvehicle when there exists that other vehicle, and determines that theredoes not exist a preceding vehicle when there does not exist that othervehicle. The ECU 10 sets the traveling mode of the ACC to the trailingmode when having determined that there exists a preceding vehicle, andsets the traveling mode of the ACC to the traveling mode at a constantspeed when having determined that there does not exist a precedingvehicle. The present disclosure disclosed in the present specificationis based on a premise that the traveling mode is the trailing mode (thatis, there exists a preceding vehicle), and therefore hereinafter, adescription about the trailing mode will be made and a detaileddescription about the traveling mode at a constant speed will beomitted. The ECU 10 acquires a distance to the preceding vehicle and arelative speed as a preceding vehicle information.

[Calculation of a Target Acceleration]

When there exists a preceding vehicle, the ECU 10 calculates a targetacceleration for trailing the preceding vehicle at a vehicle speed lessthan or equal to the set vehicle speed, maintaining the setinter-vehicular distance every time the predetermined calculationinterval elapses during the engine on period. The set inter-vehiculardistance and the set vehicle speed are determined based on theinformation acquired from the vehicle speed-inter-vehicular distancesetting switch 18 as the own vehicle information. The targetacceleration can be calculated by a “deviation ΔD between a distance tothe preceding vehicle (an inter-vehicular distance) and the setinter-vehicular distance” and a “relative speed V_(R) of the vehicle 100with respect to the preceding vehicle”. Specifically, the targetacceleration Gtgt is calculated in accordance with a following equation.It should be noted that K1 and K2 are predetermined positive gains(coefficients).

Gtgt=K1·ΔD+K2·V _(R)

The ECU 10 performs a control of the throttle actuator 19 (theacceleration control by the ACC) or a control of the brake actuator 20(the deceleration control by the ACC) in such a manner that anacceleration of the vehicle 100 coincides with the target accelerationcalculated. However, the target acceleration includes an upper limitacceleration and a lower limit acceleration (a negative deceleration)which have been set in advance, and the ECU 10 controls the throttleactuator 19 so that the acceleration of the vehicle 100 coincides withthe upper limit acceleration when the target acceleration exceeds theupper limit acceleration, and controls the brake actuator 20 so that theacceleration of the vehicle 100 coincides with the lower limitacceleration when the target acceleration falls below the lower limitacceleration.

[Setting of an AC Deceleration Control Flag]

As is obvious from the description above, the ECU 10 performs thedeceleration control by the ACC when the target acceleration is lessthan 0. The ACC determination uses the information indicating whether ornot the deceleration control by the ACC is being performed. Therefore,an AC deceleration control flag which is a flag indicating thisinformation is set in the first embodiment apparatus. The ECU 10 sets avalue of the AC deceleration control flag to 1 when the decelerationcontrol by the ACC is being performed, and sets the value of the ACdeceleration control flag to 0 when the deceleration control by the ACCis not being performed (that is, when the acceleration control by theACC (includes an acceleration of 0) is being performed). The ECU 10 usesthe value of the AC deceleration control flag in the ACC determination.

[Setting of an Acceleration Override (AOR) Flag]

When the driver depresses the accelerator pedal during the trailing bythe ACC, the ECU 10 calculates a required acceleration based on anaccelerator operation by the driver based on the accelerator pedaloperation amount, the vehicle speed, and the like. The ECU 10 determineswhether or not this required acceleration exceeds the targetacceleration calculated by the aforementioned method, and when thisrequired acceleration exceeds the target acceleration, controls thethrottle actuator 19 so that the acceleration of the vehicle 100coincides with the required acceleration. This is a known controlreferred to as an acceleration override control (AORC). That is, whenthe required acceleration exceeds the target acceleration, the ECU 10performs the AORC in preference to the trailing by the ACC. The ACCdetermination uses the information indicating whether or not the AORC isbeing performed. Therefore, an acceleration override (AOR) flag which isa flag indicating this information is set in the first embodimentapparatus. The ECU 10 sets a value of the AOR flag to 1 when the AORC isbeing performed, and sets the value of the AOR flag to 0 when the AORCis not being performed. The ECU 10 uses the value of the AOR flag in theACC determination.

C. ACC Determination

Subsequently, a description about the ACC determination will be made.The ACC determination is processing for determining whether “to continuethe ACC without performing the PCBC” or “to perform the PCBC and stopthe ACC” when it has been determined that the performing condition forthe PCBC (either the PBC or the LPBC) is satisfied during theperformance of the ACC. Therefore, the ECU 10 determines whether or notthe PCBC flag is 1 every time the predetermined calculation intervalelapses during the engine on period, and performs the ACC determinationwhen having determined that the PCBC flag=1 is satisfied.

A specific description will be made below. In general, when the vehicle100 faces the avoidance operation necessary situation in a case wherethe deceleration control by the ACC is being performed (that is, theAORC is not being performed), a deceleration amount based on the ACC(the deceleration control) in addition to a deceleration amount based onthe PCBC can be ensured. On the other hand, when the vehicle 100 facesthe avoidance operation necessary situation in a case where the AORC isbeing performed, a deceleration amount based on the ACC cannot beensured since the vehicle 100 is under the acceleration control. In thiscase, it is likely that a deceleration amount based on the PCBC alone isinsufficient even in the situation with the low collision risk, andtherefore it is desirable to have the driver perform the brake operationin accompany with the performance of the PCBC. Thus, the ECU 10 performsthe PCBC and stops the ACC regardless of a degree of the collision risk(that is, regardless of the PCBC being the PBC or the LPBC) when theAORC is being performed (that is, when the AOR flag=1). Thereby, itbecomes possible to surely prompt the driver to intervene in the brakecontrol.

In contrast, when the collision risk is relatively high (that is, whenthe PBC flag=1 and the LPBC flag=0) in a case where the AORC is notbeing performed (that is, in a case where the AOR flag=0. In otherwords, in a case where the trailing by the ACC is being performed), theECU 10 performs the PBC and stops the ACC. This is performed regardlessof the ACC, which is being performed at a point in time when theperforming condition for the PBC has been determined to be satisfied, isthe acceleration control or the deceleration control (that is,regardless of the AC deceleration control flag being 1 or 0). With thisconfiguration also, it becomes possible to surely prompt the driver tointervene in the brake control.

On the one hand, when the collision risk is relatively low and “thedeceleration control by the ACC is being performed at a point in timewhen the performing condition for the LPBC has been determined to hesatisfied (that is, the LPBC flag=1 and the AC deceleration controlflag=1)” in a case where the AORC is not being performed (that is, in acase where the AOR flag=0. In other words, in a case where the trailingby the ACC is being performed), the ECU 10 continues the ACC withoutperforming the LPBC. Thereby, a possibility of giving a strange andannoying feeling to the driver stemmed from the LPBC being performed andthe ACC being stopped contrary to the driver's expectation can bereduced.

On the other hand, when the collision risk is relatively low but “theacceleration control by the ACC is being performed at a point in timewhen the performing condition for the LPBC has been determined to besatisfied (that is, the LPBC flag=1 and the AC deceleration controlflag=0)” in a case where the AORC is not being performed (that is, in acase where the AOR flag=0. In other words, in a case where the trailingby the ACC is being performed), a deceleration amount based on the ACCcannot be ensured, and thereby it is likely that a deceleration amountbased on the LPBC alone is insufficient even in the situation with thelow collision risk. Therefore, in such a case as mentioned above, theECU 10 performs the LPBC and stops the ACC. Accordingly, it becomespossible to surely prompt the driver to intervene in the brake control.

<Control Flow of the First Embodiment Apparatus>

Next, a description about a control flow of the first embodimentapparatus will be made. The CPU of the vehicle control ECU 10 of thefirst embodiment apparatus is configured to perform routines shown byflowcharts in FIG. 5 through FIG. 9 every time the predeterminedcalculation interval elapses during the engine on period.

When a predetermined timing arrives, the CPU starts processing with astep 500 in FIG. 5 and performs processing of a following step 502.

Step 502: The CPU performs processing of setting a value of the PCBCflag. In the routine in FIG. 5, the CPU performs the routine shown bythe flowchart in FIG. 6 at the step 502. That is, the CPU proceeds tothe step 502, and subsequently starts processing with a step 600 in FIG.6 to perform processing of a following step 602.

Step 602: The CPU acquires the own vehicle information of the vehicle100 (the vehicle speed, the accelerator pedal operation amount, thebrake pedal operation amount, the yaw rate, the state of the ACC switch17 and the state of the vehicle speed-inter-vehicular distance settingswitch 18) as mentioned above, and stores this information in the RAM ofthe ECU 10.

Subsequently, the CPU proceeds to a step 604 to determine whether or notthere exist more than or equal to one target objects. When havingdetermined that there exist such target objects, the CPU makes an “Yes”determination at the step 604 and performs processing of following step606 to step 610 in this order.

Step 606: The CPU acquires the target object information of each of thetarget objects (the distance, the azimuth, and the relative speed) asmentioned above, and stores this information in the RAM of the ECU 10.

Step 608: The CPU calculates, for each of the target objects having thetarget object information acquired at the step 606, a time-to-collision(TTC) to the target object by dividing the distance to the target objectby the relative speed, and stores the value in the RAM of the ECU 10.

Step 610: The CPU selects a target object with a minimum TTC of the TTCscalculated at the step 608 (hereinafter, this target object is alsoreferred to as a “selected target object”), and labels the target objectinformation of this selected target object, which is one of the targetobject informations stored in the RAM of the ECU 10 at the step 606, as“selected target object information”.

Subsequently, the CPU proceeds to a step 612 to determine whether or notthe selected target object selected at the step 610 is a pedestrian or abicycle based on the selected target object information. When havingdetermined that the selected target object is neither a pedestrian nor abicycle (that is, when having determined that the selected target objectis an other vehicle), the CPU makes a “No” determination at the step 612and performs processing of a following step 613.

Step 613: The CPU calculates a lap rate LR with the selected targetobject determined to be an other vehicle at the step 612, and stores thevalue in the RAM of the ECU 10.

Next, the CPU proceeds to a step 614 to determine whether or not the laprate LR calculated at the step 613 is more than or equal to the firstlap rate threshold LRth1. When having determined that LR≥LRth1 issatisfied, the CPU makes an “Yes” determination at the step 614 (thatis, determines that the lap rate LR corresponds to at least the lowlap), and proceeds to a following step 616.

At the step 616, the CPU determines whether or not the TTC to theselected target object (an other vehicle) is less than the first timethreshold TTCth1. When having determined that TTC<TTCth1 is satisfied,the CPU makes an “Yes” determination at the step 616 (that is,determines that the performing condition for the PCB is satisfied), andproceeds to a step 620 described later.

On the other hand, when having determined that the selected targetobject is a pedestrian or a bicycle at the step 612, the CPU makes an“Yes” determination at the step 612, and proceeds to a following step618.

At the step 618, the CPU determines whether or not the TTC to theselected target object (a pedestrian or a bicycle) is less than thesecond time threshold TTCth2. When having determined that TTC<TTCth2 issatisfied, the CPU makes an “Yes” determination at the step 618 (thatis, determines that the performing condition for the PCBC is satisfied),and proceeds to the following step 620.

Step 620: The CPU sets the value of the PCBC flag to 1 to store thevalue in the RAM of the ECU 10. Thereafter the CPU proceeds to a step504 in FIG. 5 via a step 624.

In contrast, when having determined that there do not exist any targetobjects at the step 604, the CPU makes a “No” determination at the step604 (that is, determines that there does not exist a target of the PCBC(a target of the PBC and the LPBC)). In addition, when having determinedthat LR≥LRth1 is not satisfied at the step 614, the CPU makes a “No”determination at the step 614 (that is, determines that the lap ratedoes not correspond to either the high lap or the low lap). Further,when having determined that TTC<TTCth1 is not satisfied at the step 616,the CPU makes a “No” determination at the step 616 (that is, determinesthat the performing condition for the PCBC is not satisfied). Similarly,when having determined that TTC<TTCth2 is not satisfied at the step 618,the CPU makes a “No” determination at the step 618 (that is, determinesthat the performing condition for the PCBC is not satisfied). In suchcases as mentioned above, the CPU proceeds to a following step 622.

Step 622: The CPU sets all values of the PCBC flag, the PBC flag, andthe LPBC flag to 0, and stores these values in the RAM of the ECU 10.Thereafter, the CPU proceeds to the step 504 in FIG. 5 via the step 624.

When the CPU proceeds to the step 504 in FIG. 5, the CPU performsprocessing of setting values of the PBC flag and the LPBC flag. In theroutine in FIG. 5, the CPU performs the routine shown by the flowchartin FIG. 7 at the step 504. That is, the CPU proceeds to the step 504 andsubsequently starts processing with a step 700 in FIG. 7 to performprocessing of a following step 702.

Step 702: The CPU determines whether or not the value of the PCBC flagis 1. When having determined that the PCBC flag=1 is satisfied, the CPUmakes an “Yes” determination at the step 702 (that is, determines thatthe performing condition for either one of the PBC or the LPBC issatisfied), and proceeds to a following step 704.

At the step 704, the CPU performs the same processing as the processingat the step 612 in FIG. 6 for the selected target object selected at thestep 610 in FIG. 6. When having determined that the selected targetobject is neither a pedestrian nor a bicycle (that is, when havingdetermined that the selected target object is an other vehicle), the CPUmakes a “No” determination at the step 704, and proceeds to a followingstep 706.

At the step 706, the CPU determines whether or not the lap rate LRcalculated at the step 613 in FIG. 6 is less than the second lap ratethreshold LRth2. When having determined that LR<LRth2 is satisfied, theCPU makes an “Yes” determination at the step 706 (that is, determinesthat the lap rate LR corresponds to the low lap), and performsprocessing of a following step 708.

Step 708: The CPU identifies a steering avoidance limit time T_(S)corresponding to the lap rate LR calculated at the step 613 in FIG. 6 byreferring to the graph shown in FIG. 3 stored in the memory (ROM). TheCPU sets the steering avoidance limit time T_(S) identified as the thirdtime threshold TTCth3, and stores in the RAM of the ECU 10.

Next, the CPU proceeds to a step 710 to determine whether or not the TTCto the selected target object (an other vehicle) is more than or equalto the third time threshold TTCth3 set at the step 708. When havingdetermined that TTC≥TTCth3 is satisfied, the CPU makes an “Yes”determination at the step 710 (that is, determines that the performingcondition for the LPBC is satisfied), and proceeds to a step 714described later.

On the one hand, when having determined that the selected target objectis a pedestrian or a bicycle at the step 704, the CPU makes an “Yes”determination at the step 704, and proceeds to a following step 712.

At the step 712, the CPU determines whether or not the TTC to theselected target object (a pedestrian or a bicycle) is more than or equalto the fourth time threshold TTCth4. When having determined thatTTC≥TTCth4 is satisfied, the CPU makes an “Yes” determination at thestep 712 (that is, determines that the performing condition for the LPBCis satisfied), and proceeds to the following step 714.

Step 714: The CPU sets the value of the LPBC flag to 1 to store thevalue in the RAM of the ECU 10. Thereafter, the CPU proceeds to a step506 in FIG. 5 via a step 718.

On the other hand, when having determined that LR<LRth2 is not satisfiedat the step 706, the CPU makes a “No” determination at the step 706(that is, determines that the lap rate LR corresponds to the high lap).In addition, when having determined that TTC≥TTCth3 is not satisfied atthe step 710, the CPU makes a “No” determination at the step 710 sincethe selected target object is a vehicle, the lap rate LR corresponds tothe low lap, and TTC<TTCth3 is satisfied (that is, determines that theperforming condition for the PBC is satisfied). Further, when havingdetermined that TTC≥TTCth4 is not satisfied at the step 712, the CPUmakes a “No” determination at the step 712 since the selected targetobject is a pedestrian or a bicycle and TTC<TTCth4 is satisfied (thatis, determines that the performing condition for the PBC is satisfied).In such cases as mentioned above, the CPU performs processing of afollowing step 716.

Step 716: The CPU sets the value of the PBC flag to 1, and stores thevalue in the RAM of the ECU 10. Thereafter, the CPU proceeds to the step506 in FIG. 5 via the step 718.

In contrast, when having determined that the PCBC flag=1 is notsatisfied (that is, the PCBC flag=0 is satisfied) at the step 702, theCPU makes a “No” determination at the step 702 to proceeds to the step506 in FIG. 5 via the step 718. In this case, the values of the PBC flagand the LPBC flag have been both set to 0 (refer to the step 622 in FIG.6).

When the CPU proceeds to the step 506 in FIG. 5, the CPU determineswhether or not the ACC switch 17 is in the one state based on the ownvehicle information acquired at the step 602 in FIG. 6. When havingdetermined that the ACC switch 17 is in the one state, the CPU makes an“Yes” determination at the step 506 (that is, determines that the ACC isbeing performed), and perform processing of a following step 508.

Step 508: The CPU performs processing of setting values of the AOR flagand the AC deceleration control flag. In the routine in FIG. 5, the CPUperforms the routine shown by the flowchart in FIG. 8 at the step 508.That is, the CPU proceeds to the step 508, and subsequently startsprocessing with a step 800 in FIG. 8 to proceed to a following step 802.

At the step 802, the CPU determines whether or not the AORC is beingperformed as mentioned above. When having determined that the AORC isbeing performed, the CPU makes an “Yes” determination at the step 802,and performs processing of a following step 804.

Step 804: The CPU sets the value of the AOR flag to 1 and stores thevalue in the RAM of the ECU 10. Thereafter, the CPU proceeds to a step510 in FIG. 5 via a step 818. That is, the AORC is performed inpreference to the trailing by the ACC, and therefore when havingdetermined that the AORC is being performed, the CPU does not performprocessing of setting the value of the AC deceleration control flag(instead, uses the value at the previous calculation interval).

On the other hand, when having determined that the AORC is not beingperformed at the step 802, the CPU makes a “No” determination at thestep 802, and performs processing of a following step 806.

Step 806: The CPU sets the value of the AOR flag to 0 to store the valuein the RAM of the ECU 10. Thereafter, the CPU performs followingprocessing of a step 808 and a step 810 in this order.

Step 808: The CPU acquires the preceding vehicle information (thedistance and the relative speed) as mentioned above, and stores thisinformation in the RAM of the ECU 10.

Step 810: The CPU calculates a target acceleration for trailing thepreceding vehicle at a vehicle speed less than or equal to the setvehicle speed, maintaining the set inter-vehicular distance, and storesthe calculated value in the RAM of the ECU 10.

Subsequently, the CPU proceeds to a step 812 to determine whether or notthe target acceleration calculated at the step 810 is less than 0 (thatis, a negative value). When having determined that the targetacceleration<0 is satisfied, the CPU makes an “Yes” determination at thestep 812 (that is, determines that the deceleration control by the ACCis being performed), and performs processing of a following step 814.

Step 814: The CPU sets the value of the AC deceleration control flag to1, and stores the value in the RAM of the ECU 10. Thereafter, the CPUproceeds to a step 510 in FIG. 5 via the step 818.

In contrast, when having determined that the target acceleration<0 isnot satisfied (that is, the target acceleration≥0 is satisfied) at thestep 812, the CPU makes a “No” determination at the step 812 (that is,determines that the acceleration control by the ACC is being performed),and performs processing of a following step 816.

Step 816: The CPU sets the value of the AC deceleration control flag to0, and stores the value in the RAM of the ECU 10. Thereafter, the CPUproceeds to the step 510 in FIG. 5 via the step 818.

When the CPU proceeds to the step 510 in FIG. 5, the CPU determineswhether or not the value of the PCBC flag set at the step 502 is 0. Whenhaving determined that the PCBC flag=1 is satisfied, the CPU makes an“Yes” determination at the step 510 (that is, determines that theperforming condition for the PCBC is satisfied), and performs processingof a following step 512.

Step 512: When the value of the PCBC flag is set to 1 during theperformance of the ACC, the CPU performs an ACC determination processingfor determining whether “to continue the ACC without performing thePCBC” or “to perform the PCBC and stop the ACC”. In the routine in FIG.5, the CPU performs the routine shown by the flowchart in FIG. 9 at thestep 512. That is, the CPU proceeds to the step 512, and subsequentlystarts processing with a step 900 in FIG. 9 to proceed to a followingstep 901.

At the step 901, the CPU determines whether or not the value of the AORflag set at the step 508 in FIG. 5 is 1. When having determined that theAOR flag=1 is not satisfied, the CPU makes a “No” determination at thestep 901 (that is, determines that the AORC is not being performed butthe trailing by the ACC is being performed), and proceeds to a followingstep 902.

At the step 902, the CPU determines whether or not the value of the LPBCflag set at the step 504 in FIG. 5 is 1. When having determined that theLPBC flag=1 is satisfied, the CPU makes an “Yes” determination at thestep 902 (that is, determines that the performing condition for the LPBCis satisfied during the performance of the ACC), and proceeds to afollowing step 904.

At the step 904, the CPU determines whether or not the value of the ACdeceleration control flag set at the step 508 in FIG. 5 is 1. Whenhaving determined that the AC deceleration control flag=1 is satisfied,the CPU makes an “Yes” determination at the step 904 (that is,determines that the deceleration control by the ACC is being performedat a point in time when the performing condition for the LPBC has beendetermined to be satisfied), and performs processing of a following step906.

Step 906: The CPU does not perform the LPBC but continues the ACC.Thereafter, the CPU proceeds to a step 514 in FIG. 5 via a step 910 totentatively terminate the present routine.

In contrast, when having determined that the AOR flag=1 is satisfied atthe step 901, the CPU makes an “Yes” determination at the step 901 (thatis, determines that the AORC is being performed at a point in time whenthe performing condition for the PCBC has been determined to besatisfied). In addition, when having determined that the LPBC flag=1 isnot satisfied (that is, the LPBC flag=0 and the PBC flag=1 are bothsatisfied) at the step 902, the CPU makes a “No” determination at thestep 902 (that is, determines that the PBC is started during theperformance of the trailing by the ACC). Further, when having determinedthat the AC deceleration control flag=1 is not satisfied at the step904, the CPU makes a “No” determination at the step 904 (that is,determines that the acceleration control by the ACC is being performedat a point in time when the performing condition for the LPBC has beendetermined to be satisfied). In such cases as mentioned above, the CPUperforms processing of a following step 908.

Step 908: The CPU stops the ACC. Specifically, when an “Yes”determination has been made at the step 901, the CPU performs the PBCand stops the ACC when the PBC flag=1 is satisfied, while performs theLPBC and stops the ACC when the LPBC flag=1 is satisfied. When a “No”determination has been made at the step 902, the CPU performs the PBCand stops the ACC. When a “No” determination has been made at the step904, the CPU performs the LPBC and stops the ACC. Thereafter, the CPUproceeds to the step 514 in FIG. 5 via the step 910 to tentativelyterminate the present routine.

On the other hand, when having determined that the ACC switch 17 is inthe off state at the step 506 in FIG. 5, the CPU makes a “No”determination at the step 506 (that is, determines that the ACC is notbeing performed), and proceeds to the step 514 to tentatively terminatethe present routine. In addition, when having determined that the PCBCflag=1 is not satisfied at the step 510, the CPU makes a “No”determination at the step 510 (that is, determines that although the ACCis being performed, the performing condition for the PCBC is notsatisfied), and proceeds to the step 514 to tentatively terminate thepresent routine.

Effects of the first embodiment apparatus will be described. In thefirst embodiment apparatus, the PCBC is not performed but the ACCcontinues to be performed when following conditions a and b aresatisfied in a case of a control object being a preceding vehicle, orwhen a following condition c is satisfied in a case of a control objectbeing a pedestrian or a bicycle, in a case where the decelerationcontrol by the ACC is being performed at a point in time when theperforming condition for the PCBC has been determined to be satisfiedduring the performance of the ACC, this performing condition beingTTC<TTCth1 in a case of a control object being a preceding vehicle andTTC<TTCth2 in a case of a control object being a pedestrian or abicycle.

-   In a case of an object subject to the PCBC being a preceding vehicle-   (Condition a) LRth1≤LR<LRth2-   (Condition b) TTCth3≤TTC-   In a case of an object subject to the PCBC being a pedestrian or a    bicycle-   (Condition c) TTCth4≤TTC

A case where the conditions a and b are satisfied or the condition c issatisfied in a case when the deceleration control by the ACC is beingperformed at a point in time when the performing condition for the PCBChas been determined to be satisfied is highly likely to be a case whereTTC<TTCth1 (in a case of a control object being a preceding vehicle) orTTC<TTCth2 (in a case of a control object being a pedestrian or abicycle) is satisfied, in the “situation where the driver does notconsider oneself to be in the avoidance operation necessary situation”or in the “situation where the driver recognizes (considers) oneself tobe in the avoidance operation necessary situation, however, the driverhas an intention to avoid a collision by the steering wheel operationinstead of the brake operation”. That is, the case above is highlylikely to be a case where the driver does not assume the PCBC to beperformed and rather expects the performance of the ACC to be continued.According to the first embodiment apparatus, the PCBC is not performedbut the performance of the ACC is continued in such a case. Therefore,an occurrence of a situation where the PCBC is performed and the ACC isstopped contrary to the drivers expectation can be suppressed, and apossibility of giving a strange and annoying feeling to the driver canbe reduced.

In addition, in the first embodiment apparatus, the PCBC is notperformed but the ACC continues to be performed also when the aboveconditions a and b are satisfied in a case of a control object being apreceding vehicle, or when the above condition c is satisfied in a caseof a control object being a pedestrian or a bicycle, in a case where theAORC is being performed at a point in time when the performing conditionfor the PCBC has been determined to be satisfied.

A case where the conditions a and b are satisfied or the condition c issatisfied in a case when the AORC is being performed at a point in timewhen the performing condition for the PCBC has been determined to besatisfied is highly likely to be a case where TTC<TTCth1 (in a case of acontrol object being a preceding vehicle) or TTC<TTCth2 (in a case of acontrol object being a pedestrian or a bicycle) is satisfied in the“situation where the driver does not consider oneself to be in theavoidance operation necessary situation”. That is, the case above ishighly likely to be a case where the driver does not assume the PCBC tobe performed and rather expects the performance of the ACC to becontinued. According to the first embodiment apparatus, in such a casealso, the PCBC is not performed but the performance of the ACC iscontinued. Therefore, a possibility of giving a strange and annoyingfeeling to the driver can be more reduced.

Further, in the first embodiment apparatus, the PCBC consists of twosteps, the PBC and the LPBC. In a case where an object subject to thePCBC is a preceding vehicle and the performing condition for the PCBC issatisfied, the braking force by the LPBC is applied when the aboveconditions a and b are satisfied (however, the LPBC is not performedwhen the deceleration control by the ACC is being performed at a pointin time when the performing condition for the PCBC has been determinedto be satisfied), and the braking force by the PBC is applied when atleast one of the conditions a and b is not satisfied. Besides, in a casewhere an object subject to the PCBC is a pedestrian or a bicycle and theperforming condition for the PCBC is satisfied, the braking force by theLPBC is applied when the above condition c is satisfied (however, theLPBC is not performed when the deceleration control by the ACC is beingperformed at a point in time when the performing condition for the PCBChas been determined to be satisfied), and the braking force by the PBCis applied when the condition c is not satisfied.

According to the above configuration, when it is highly likely that thedriver does not assume the PCBC to be performed, the light braking forceby the LPBC is applied or the LPBC itself is not performed. Therefore, adegree to interfere with the driving operation by the driver can bereduced. In addition, in a case where it turned out that the driver wasactually in the avoidance operation necessary situation, when the LPBCis performed, a certain amount of deceleration amount can be ensuredcompared with a configuration where no braking force is applied sincethe light braking force is applied to the vehicle 100, and when the LPBCis not performed, on the other hand, a deceleration amount based on thedeceleration control by the ACC can be ensured. Thus, in both cases, acollision avoidance or reduction of a collision damage can be properlyrealized.

Further, the first embodiment apparatus is configured to change thethird time threshold TTCth3 in such a manner that the third timethreshold TTCth3 becomes smaller as the lap rate LR becomes low.According to this configuration, even though the TTC to the precedingvehicle becomes shorter (that is, even though the vehicle 100 approachesthe preceding vehicle closer), as the lap rate LR becomes lower, thePCBC becomes more difficult to be performed and the ACC becomes easierto be continued. It is highly likely that as the lap rate LR becomeslower, a distance to the preceding vehicle becomes shorter for a purposeof the vehicle 100 passing the preceding vehicle or the driver of thevehicle 100 avoiding a collision with the preceding vehicle by thesteering wheel operation. Therefore, according to the configurationabove, a possibility that the PCBC is performed and the ACC is stoppedcontrary to the driver's expectation can be further reduced.

Second Embodiment

Next, a vehicle control apparatus (a second embodiment apparatus)according to a second embodiment of the present disclosure will bedescribed below. In the second embodiment apparatus, only an ACCdetermination processing at a step 512 in FIG. 5 differs from that inthe first embodiment apparatus. Specifically, in the first embodimentapparatus, when it is determined that the AORC is being performed at apoint in time the performing condition for the PCBC has been determinedto be satisfied, the PCBC is performed and the ACC is stopped regardlessof the types of the PCBC (refer to an “Yes” at the step 901 in FIG. 9).In contrast, in the second embodiment apparatus, when a type of the PCBCis the LPBC in a case where it is determined that the AORC is beingperformed at a point in time the performing condition for the PCBC hasbeen determined to be satisfied, this LPBC is not performed but the ACCis continued (refer to an “Yes” at a step 1004 in FIG. 10 which will bedescribed later). In the following, an ACC determination processing(refer to the step 512 in FIG. 5) of the second embodiment apparatuswill be described.

Step 512: The CPU performs the ACC determination processing. In aroutine of the second embodiment apparatus in FIG. 5, the CPU proceedsto the step 512, and subsequently starts processing with a step 1000 inFIG. 10 to proceed to a following step 1002.

At the step 1002, the CPU determines whether or not the value of theLPBC flag set at the step 504 in FIG. 5 is 1. When having determinedthat the LPBC flag=1 is satisfied, the CPU makes an “Yes” determinationat the step 1002 (that is, determines that the performing condition forthe LPBC is satisfied during the performance of the ACC), and proceedsto the following step 1004.

At the step 1004, the CPU determines whether or not the value of the AORflag set at the step 508 in FIG. 5 is 1. When having determined that theAOR flag=1 is satisfied, the CPU makes an “Yes” determination at thestep 1004 (that is, determines that the AORC is being performed at apoint in time when the performing condition for the LPBC has beendetermined to be satisfied), and performs processing of a step 1008which will be described later.

On the other hand, when having determined that the AOR flag−1 is notsatisfied (that is, the AOR flag=0 is satisfied) at the step 1004, theCPU makes a “No” determination at the step 1004 (that is, determinesthat the trailing by the ACC is being performed in place of the AORC ata point in time when the performing condition for the LPBC has beendetermined to be satisfied), and proceeds to a following step 1006.

At the step 1006, the CPU determines whether or not the value of the ACdeceleration control flag set at the step 508 in FIG. 5 is 1. Whenhaving determined that the AC deceleration control flag=1 is satisfied,the CPU makes an “Yes” determination at the step 1006 (that is,determines that the deceleration control by the ACC is being performedat a point in time when the performing condition for the LPBC has beendetermined to be satisfied), and performs processing of a following step1008.

Step 1008: The CPU determines not to perform the LPBC but to continuethe ACC. Thereafter, the CPU proceeds to the step 514 in FIG. 5 via astep 1012 to tentatively terminate the present routine.

In contrast, when having determined that the LPBC flag=1 is notsatisfied (that is, the LPBC flag=0 and the PBC flag=1 are bothsatisfied) at the step 1002, the CPU makes a “No” determination at thestep 1002 (that is, determines that the PBC is performed during theperformance of the ACC). In addition, when having determined that the ACdeceleration control flag=1 is not satisfied at the step 1006, the CPUmakes a “No” determination at the step 1006 (that is, determines thatthe acceleration control by the ACC is being performed at a point intime when the performing condition for the LPBC has been determined tobe satisfied). In such cases as mentioned above, the CPU performsprocessing of a following step 1010.

Step 1010: The CPU determines to perform the PCBC (the PBC or the LPBC)and to stop the ACC. Thereafter, the CPU proceeds to the step 514 inFIG. 5 via the step 1012 to tentatively terminate the present routine.

With this configuration also, the similar effects to the firstembodiment apparatus can be obtained.

In the first embodiment apparatus, when it is determined that the AORCis being performed at a point in time when the performing condition forthe PCBC has been determined to be satisfied, the PCBC is performed andthe ACC is stopped. The reason why such a configuration is adopted isbecause the AORC is an acceleration control and therefore a decelerationamount based on the ACC cannot be ensured, resulting in that adeceleration amount may not be able to be sufficiently ensured even inthe situation with the low collision risk.

However, from a different perspective, it can be also considered thatthe AORC is an acceleration control based on a driver's intention andtherefore it is highly likely that the driver intervenes in the brakecontrol on his/her own initiative when facing the avoidance operationnecessary situation, resulting in that a sufficient deceleration amountcan be ensured. Hence, in the second embodiment apparatus, when a typeof the PCBC is the LPBC in a case where it is determined that the AORCis being performed at a point in time when the performing condition forthe PCBC has been determined to be satisfied, the LPBC is not performedbut the ACC is continued.

According to the configuration above, when facing the avoidanceoperation necessary situation with a relatively low collision risk, adeceleration amount based on the brake operation by the driver can beensured due to the independent intervention in the brake control by thedriver even though the LPBC is not performed. Therefore, it becomesunnecessary to stop the ACC for a purpose of prompting the driver tointervene in the brake control. Thus, according to the configuration ofthe second embodiment apparatus, a deceleration amount can besufficiently ensured in the avoidance operation necessary situation withthe relatively low collision risk, and a possibility of giving a strangeand annoying feeling to the driver stemmed from the LPBC being performedand the ACC being stopped contrary to the driver's expectation can befurther reduced.

Third Embodiment

Subsequently, a vehicle control apparatus (a third embodiment apparatus)according to a third embodiment of the present disclosure will bedescribed below. In the third embodiment apparatus, only an ACCdetermination processing at a step 512 in FIG. 5 differs from that inthe first embodiment apparatus. Specifically, the third embodimentapparatus differs from the first embodiment apparatus in that either oneof the PBC or the LPBC never fails to be performed when the performingcondition for the PCBC is satisfied during the performance of the ACC,that the performance of the ACC is stopped when the PCBC is startedduring the performance of the ACC, and that the ACC is automaticallyresumed after the performance of the LPBC when the deceleration controlby the ACC is being performed at a point in time when the performingcondition for the LPBC has been determined to be satisfied. Hereinafter,differences from the first embodiment apparatus will be mainlydescribed.

<Summary of Operation of Third Embodiment Apparatus>

The third embodiment apparatus stops the performance of the ACC when thePCBC is started during, the performance of the ACC at the trailing mode.Besides, the third embodiment apparatus determines whether or not toautomatically resume the ACC when the performance of the PCBC isfinished (ACC determination). If the ACC is resumed automatically afterthe performance of the PCBC, there is a possibility that the driveroverestimates a performance of the third embodiment apparatus and doesnot intervene in the brake control after the performance of the PCBC.Therefore, in the situation where the collision risk is expected to berelatively high, it is desired to prompt the driver to surely intervenein the brake control by continuing to stop the ACC after the performanceof the PCBC. Thus, when a type of the PCBC is the PBC (that is, acontrol performed when the collision risk is relatively high), the thirdembodiment apparatus determines that the PBC alone is insufficient, andcontinues to stop the ACC after the performance of the PBC.

On the other hand, in a configuration where the ACC always continues tobe stopped after the performance of the PCBC, if the performingcondition for the PCBC happens to be satisfied contrary to the driver'sintention, the ACC will not be automatically resumed contrary to thedriver's expectation, which is not desirable.

As described above by referring to FIG. 4A to FIG. 4C, the collisionrisk is expected to be relatively low in a “case where the PCBC happensto be performed contrary to the driver's intention”. Therefore, when atype of this PCBC is the LPBC (that is, a control performed when thecollision risk is relatively low), if the deceleration control by theACC is being performed at a point in time when the performing conditionfor this LPBC has been determined to be satisfied, the third embodimentapparatus automatically resumes the ACC when this LPBC is finished.Besides, if the deceleration control by the ACC is not being performedat a point in time when the performing condition for this LPBC has beendetermined to be satisfied (that is, if the acceleration control by theACC or the acceleration override control is being performed at thispoint in time), the third embodiment apparatus continues to stop the ACCalso after this LPBC is finished. That is, assuming that the performingcondition for the LPBC has been determined to be satisfied in theexamples of FIG. 4A through FIG. 4C, the deceleration control by the ACCis being performed at a point in time when the performing condition forthe LPBC has been determined to be satisfied, and therefore the ACC willbe resumed automatically when the LPBC is finished. Thus, it can beprevented that the ACC continues to be stopped after the performance ofthe LPBC contrary to the driver's expectation.

Based on the summary mentioned above, hereinafter, points different fromthe first embodiment apparatus concerning the PCBC and the ACCdetermination processing will be mainly described in detail.

<Detail of Operation of the Third Embodiment Apparatus> D. PCB Control[LPBC in a Case When the Target Object is an Other Vehicle]

In a case of the low lap, when the TTC is more than or equal to thethird time threshold TTCth3 and less than the first time thresholdTTCth1, the collision risk is relatively low since the steeringavoidance is possible although there is still some collision possibilitybecause the brake avoidance is difficult. If a braking force equal tothe braking force of the PBC is applied in such a case, the interferencewith the driving operation by the driver occurs in a case where thedriver has an intention to avoid a collision by the steering wheeloperation, resulting in giving a strange or annoying feeling to thedriver. In addition, when the vehicle 100 changes a traffic lane for apurpose of passing the other vehicle, the vehicle 100 may deviate in thevehicle width direction with respect to the other vehicle, temporarilyapproaching the other vehicle, and as a result, the lap rate LR maybecome low (that is, the low lap), and the TTC may become more than orequal to the third time threshold TTCth3 and less than the first timethreshold TTCth1. In this case also, if a braking force equal to thebraking force of the PBC is applied, this control may be regarded as anunnecessary control, causing a strange or annoying feeling to the driversince the driver does not consider oneself to be in the situation wherea collision avoidance with the other vehicle is necessary. However, ifany braking force is not applied in order to resolve this, adeceleration amount cannot be sufficiently ensured when it turned outthat the PCBC was actually necessary.

Therefore, when the TTC is more than or equal to the third timethreshold TTCth3 and less than the first time threshold TTCth1 in a caseof the low lap, the ECU 10 determines that the performing condition forthe LPBC for applying a light braking force is satisfied, and performsthe LPBC. That is, the ECU 10 performs two stages of the PCBC in case ofthe low lap. In some embodiments, the braking force of the LPBC is setto such a value (magnitude) that the driver can accept the performanceof the LPBC even in a “case where the driver of the vehicle 100 does notassume the PCBC to be performed”.

[PBC and LPBC in a Case When the Target Object is a Pedestrian or aBicycle]

When the TTC is less than the fourth time threshold TTCth4, the ECU 10determines that the performing condition for the PBC is satisfied toperform the PBC, and when the TTC is more than or equal to the fourthtime threshold TTCth4 and less than the second time threshold TTCth2,the ECU 10 determines that the performing condition for the LPBC issatisfied to perform the LPBC. By adopting a configuration where theLPBC is switched to the PBC in accompany with a decrease in the TTC, apossibility that the PCBC is regarded as an unnecessary control by thedriver can be lowered. Besides, a deceleration amount required when itturned out that the PCBC was actually necessary can be ensured.

[Setting of a PCBC Flag]

When having determined that the performing condition for the PCBC issatisfied, the ECU 10 sets a value of the PCBC flag to 1, and performsthe PCBC (that is, either one of the PBC or the LPBC). On the otherhand, when having determined that the performing condition for the PCBCis not satisfied, the ECU 10 sets the value of the PCBC flag to 0, anddoes not perform the PCBC. That is, the value of the PCBC flag being 1means, in the first embodiment apparatus, that the performing conditionfor the PCBC is satisfied, whereas in the third embodiment apparatus,that the performing condition for the PCBC is satisfied and as a result,the PCBC is performed.

[Setting of a LPBC Flag]

When having determined that the performing condition for the LPBC issatisfied, the ECU 10 sets a value of the LPBC flag to 1, and performsthe LPBC. On the other hand, when having determined that the performingcondition for the LPBC is not satisfied, the ECU 10 does not perform theLPBC. That is, the value of the LPBC flag being 1 means, in the firstembodiment apparatus, that the performing condition for the LPBC issatisfied, whereas in the third embodiment apparatus, that theperforming condition for the LPBC is satisfied and as a result, the LPBCis performed.

E. ACC Determination

An ACC determination is processing for determining whether or not toautomatically resume the ACC when the PCBC is finished in a case whenthe PCBC (either one of the PBC or the LPBC) is started during theperformance of the ACC. Therefore, the ECU 10 determines whether or notthe PCBC flag is 1 every time the predetermined calculation intervalelapses during the engine on period, and performs the ACC determinationwhen having determined that the PCBC flag=1 is satisfied.

A specific description will be made below. When the AORC is beingperformed (that is, when the AOR flag=1), the ECU 10 continues to stopthe ACC (more specifically, continues to stop the ACC, this ACC beingstopped when the PCBC is started, also after the PCBC is finished)regardless of a degree of the collision risk (that is, regardless of thePCBC being the PBC or the LPBC). Thereby, it becomes possible to surelyprompt the driver to intervene in the brake control.

In contrast, when the collision risk is relatively high (that is, whenthe PBC flag=1 and the LPBC flag=0) in a case where the AORC is notbeing performed (that is, in a case where the AOR flag=0. In otherwords, in a case where the trailing by the ACC is being performed), theECU 10 continues to stop the ACC (more specifically, continues to stopthe ACC, this ACC being stopped when the PBC is started, also after thePBC is finished). This is performed regardless of whether the ACC whichis being performed at a point in time when the performing condition forthe PBC has been determined to be satisfied is the acceleration controlor the deceleration control (that is, regardless of whether the ACdeceleration control flag is 1 or 0). With this configuration also, itbecomes possible to surely prompt the driver to intervene in the brakecontrol.

On the one hand, when the collision risk is relatively low and “thedeceleration control by the ACC is being performed at a point in timewhen the performing condition for the LPBC has been determined to besatisfied (that is, the LPBC flag=1 and the AC deceleration controlflag=1)” in a case where the AORC is not being performed (that is, in acase where the AOR flag=0. In other words, in a case where the trailingby the ACC is being performed), the ECU 10 automatically resumes the ACCwhen the LPBC is finished. Thereby, a possibility of giving a strangeand annoying feeling to the driver stemmed from the ACC continuing to bestopped after the LPBC is finished contrary to the driver's expectationcan be reduced.

On the other hand, when the collision risk is relatively low but “theacceleration control by the ACC is being performed at a point in timewhen the performing condition for the LPBC has been determined to besatisfied (that is, the LPBC flag=1 and, the AC deceleration controlflag=0)” in a case where the AORC is not being performed (that is, in acase where the AOR flag=0. In other words, in a case where the trailingby the ACC is being performed), a deceleration amount based on the ACCcannot be ensured, and thereby it is likely that a deceleration amountbased on the LPBC alone is insufficient even in the situation with thelow collision risk. Therefore, in such a case as mentioned above, theECU 10 continues to stop the ACC (more specifically, continues to stopthe ACC, this ACC being stopped when the LPBC is started, also after theLPBC is finished). Accordingly, it becomes possible to surely prompt thedriver to intervene in the brake control.

Next, the ACC determination processing (refer to the step 512 in FIG. 5)of the third embodiment apparatus will be described.

Step 512: The CPU performs the ACC determination processing. In aroutine of the third embodiment apparatus in FIG. 5, the CPU proceeds tothe step 512, and subsequently starts processing with a step 1100 inFIG. 11 to proceed to a following step 1101.

At the step 1101, the CPU determines whether or not the value of the AORflag set at the step 508 in FIG. 5 is 1. When having determined that theAOR flag=1 is not satisfied, the CPU makes a “No” determination at thestep 1101 (that is, determines that the AORC is not being performed butthe trailing by the ACC is being performed), and proceeds to a followingstep 1102.

At the step 1102, the CPU determines whether or not the value of theLPBC flag set at the step 504 in FIG. 5 is 1. When having determinedthat the LPBC flag=1 is satisfied, the CPU makes an “Yes” determinationat the step 1102 (that is, determines that the LPBC is started duringthe performance of the ACC), and proceeds to a following step 1104.

At the step 1104, the CPU determines whether or not the value of the ACdeceleration control flag set at the step 508 in FIG. 5 is 1. Whenhaving determined that the AC deceleration control flag=1 is satisfied,the CPU makes an “Yes” determination at the step 1104 (that is,determines that the deceleration control by the ACC is being performedat a point in time when the performing condition for the LPBC has beendetermined to be satisfied), and performs processing of a following step1106.

Step 1106: The CPU determines to automatically resume the ACC when theLPBC is finished. Thereafter, the CPU proceeds to the step 514 in FIG. 5via a step 1110 to tentatively terminate the present routine.

In contrast, when having determined that the AOR flag=1 is satisfied atthe step 1101, the CPU makes an “Yes” determination at the step 1101(that is, determines that the AORC is being performed at a point in timewhen the performing condition for the PCBC has been determined to besatisfied). In addition, when having determined that the LPBC flag=1 isnot satisfied (that is, the LPBC flag=0 and the PBC flag=1 are bothsatisfied) at the step 1102, the CPU makes a “No” determination at thestep 1102 (that is, determines that the PBC is started during theperformance of the trailing by the ACC). Further, when having determinedthat the AC deceleration control flag=1 is not satisfied at the step1104, the CPU makes a “No” determination at the step 1104 (that is,determines that the acceleration control by the ACC is being performedat a point in time when the performing condition for the LPBC has beendetermined to be satisfied). In such cases as mentioned above, the CPUperforms processing of a following step 1108.

Step 1108: The CPU determines to continue to stop the ACC after the PCBC(the PBC or the LPBC) is finished. Thereafter, the CPU proceeds to thestep 514 in FIG. 5 via the step 1110 to tentatively terminate thepresent routine.

Effects of the third embodiment apparatus will be described. In thethird embodiment apparatus, the performance of the ACC is stopped whenit is determined that the performing condition for the PCBC is satisfiedduring the performance of the ACC, this performing condition beingTTC<TTCth1 in a case of a control object being a preceding vehicle andTTC<TTCth2 in a case of a control object being a pedestrian or abicycle, and the PCBC is started. Besides, the ACC is automaticallyresumed after the PCBC is finished, this PCBC being started during theperformance of the ACC, when following conditions a and b are satisfiedin a case of a control object being a preceding vehicle, or when afollowing condition c is satisfied in a case of a control object being apedestrian or a bicycle, in a case where the deceleration control by theACC is being performed at a point in time when the performing conditionfor the PCBC has been determined to be satisfied.

-   In a case of an object subject to the PCBC being a preceding vehicle-   (Condition a) LRth1≤LR<LRth2-   (Condition b) TTCth3≤TTC-   In a case of an object subject to the PCBC being a pedestrian or a    bicycle-   (Condition c) TTCth4≤TTC

A case where the conditions a and b are satisfied or the condition c issatisfied in a case when the deceleration control by the ACC is beingperformed at a point in time when the performing condition for the PCBChas been determined to be satisfied is highly likely to be a case wherethe driver does not expect that “the performance of the ACC continues tobe stopped also after the PCBC (the LPBC) is finished”. According to thethird embodiment apparatus, the ACC is automatically resumed after thePCBC is finished in such a case. Therefore, an occurrence of a situationwhere the ACC continues to be stopped after the PCBC is finishedcontrary to the driver's expectation can be suppressed, and apossibility of giving a strange and annoying feeling to the driver canbe reduced.

In addition, in the third embodiment apparatus, the ACC is automaticallyresumed after the PCBC is finished, this PCBC being started during theperformance of the ACC also when the above conditions a and b aresatisfied in a case of a control object being a preceding vehicle, orwhen the above condition c is satisfied in a case of a control objectbeing a pedestrian or a bicycle, in a case where the AORC is beingperformed at a point in time when the performing condition for the PCBChas been determined to be satisfied.

A case where the conditions a and b are satisfied or the condition c issatisfied in a case when the AORC is being performed at a point in timewhen the performing condition for the PCBC has been determined to besatisfied is highly likely to be a case where the driver does not expectthat “the performance of the ACC continues to be stopped also after thePCBC (the LPBC) is finished”. According to the third embodimentapparatus, the ACC is automatically resumed after the PCBC is finishedin such a case. Therefore, a possibility of giving a strange andannoying feeling to the driver can be more reduced.

Further, in the third embodiment apparatus, the PCBC consists of twosteps, the PBC and the LPBC. According to this configuration, when it ishighly likely that the driver does not assume the PCBC to be performed,the light braking force by the LPBC is applied. Therefore, a degree tointerfere with the driving operation by the driver can be reduced. Inaddition, in a case where it turned out that the driver was actually inthe avoidance operation necessary situation, a certain amount ofdeceleration amount can be ensured compared with a configuration whereno braking force is applied since the light braking force is applied tothe vehicle 100. Thus, a collision avoidance or reduction of a collisiondamage can be properly realized.

Further, the third embodiment apparatus is configured to change thethird time threshold TTCth3 in such a manner that the third timethreshold TTCth3 becomes smaller as the lap rate LR becomes low.According to this configuration, even though the TTC to the precedingvehicle becomes shorter (that is, even though the vehicle 100 approachesthe preceding vehicle closer), as the lap rate LR becomes lower, the ACCbecomes easier to be resumed after the PCBC is finished. Therefore,according to the configuration above, a possibility that the ACCcontinues to be stopped after the PCBC is finished contrary to thedriver's expectation can be further reduced.

Fourth Embodiment

Subsequently, a vehicle control apparatus (a fourth embodimentapparatus) according to a fourth embodiment of the present disclosurewill be described below. In the fourth embodiment apparatus, only an ACCdetermination processing at a step 512 in FIG. 5 differs from that inthe third embodiment apparatus. Specifically, in the third embodimentapparatus, when it is determined that the AORC is being performed at apoint in time when the performing condition for the PCBC has beendetermined to be satisfied, the ACC continues to be stopped after thePCBC is finished regardless of the types of the PCBC (refer to an “Yes”at the step 1101 in FIG. 11). In contrast, in the fourth embodimentapparatus, when a type of the PCBC is the LPBC in a case where it isdetermined that the AORC is being performed at a point in time when theperforming condition for the PCBC has been determined to be satisfied,the ACC is automatically resumed after this LPBC is finished (refer toan “Yes” at a step 1204 in FIG. 12 which will be described later).Hereinafter, a description about the ACC determination processing of thefourth embodiment apparatus (refer to the step 512 in FIG. 5) will bemade.

Step 512: The CPU performs the ACC determination processing. In aroutine of the fourth embodiment apparatus in FIG. 5, the CPU proceedsto the step 512, and subsequently starts processing with a step 1200 inFIG. 12 to proceed to a following step 1202.

At the step 1202, the CPU determines whether or not the value of theLPBC flag set at the step 504 in FIG. 5 is 1. When having determinedthat the LPBC flag=1 is satisfied, the CPU makes an “Yes” determinationat the step 1202 (that is, determines that the LPBC is performed duringthe performance of the ACC), and proceeds to the following step 1204.

At the step 1204, the CPU determines whether or not the value of the AORflag set at the step 508 in FIG. 5 is 1. When having determined that theAOR flag=1 is satisfied, the CPU makes an “Yes” determination at thestep 1204 (that is, determines that the AORC is being performed at apoint in time when the performing condition for the LPBC has beendetermined to be satisfied), and performs processing of a step 1208which will be described later.

On the other hand, when having determined that the AOR flag=1 is notsatisfied (that is, the AOR flag=0 is satisfied) at the step 1204, theCPU makes a “No” determination at the step 1204 (that is, determinesthat the trailing by the ACC is being performed in place of the AORC ata point in time when the performing condition for the LPBC has beendetermined to be satisfied), and proceeds to a following step 1206.

At the step 1206, the CPU determines whether or not the value of the ACdeceleration control flag set at the step 508 in FIG. 5 is 1. Whenhaving determined that the AC deceleration control flag=1 is satisfied,the CPU makes an “Yes” determination at the step 1206 (that is,determines that the deceleration control by the ACC is being performedat a point in time when the performing condition for the LPBC has beendetermined to be satisfied), and performs processing of a following step1208.

Step 1208: The CPU determines to automatically resume the ACC which hasbeen stopped after the LPBC is finished. Thereafter, the CPU proceeds tothe step 514 in FIG. 5 via a step 1212 to tentatively terminate thepresent routine.

In contrast, when having determined that the LPBC flag=1 is notsatisfied (that is, the LPBC flag=0 and the PBC flag=1 are bothsatisfied) at the step 1202, the CPU makes a “No” determination at thestep 1202 (that is, determines that the PBC is performed during theperformance of the ACC). In addition, when having determined that the ACdeceleration control flag=1 is not satisfied at the step 1206, the CPUmakes a “No” determination at the step 1206 (that is, determines thatthe acceleration control by the ACC is being performed at a point intime when the performing condition for the LPBC has been determined tobe satisfied). In such cases as mentioned above, the CPU performsprocessing of a following step 1210.

Step 1210: The CPU determines to continue to stop the ACC after the PCBC(the PBC or the LPBC) is finished. Thereafter, the CPU proceeds to thestep 514 in FIG. 5 via the step 1212 to tentatively terminate thepresent routine.

With this configuration also, the similar effects to the thirdembodiment apparatus can be obtained.

In the third embodiment apparatus, when it is determined that the AORCis being performed at a point in time when the performing condition forthe PCBC has been determined to be satisfied, the ACC continues to bestopped after the PCBC is finished regardless of the types of the PCBC.The reason why such a configuration is adopted is because the AORC is anacceleration control and therefore a deceleration amount based on theACC cannot be ensured, resulting in that a deceleration amount may notbe able to be sufficiently ensured even in the situation with the lowcollision risk.

However, from a different perspective, it can be also considered thatthe AORC is an acceleration control based on a driver's intention andtherefore it is highly likely that the driver intervenes in the brakecontrol on his/her own initiative when facing the avoidance operationnecessary situation, resulting in that a sufficient deceleration amountcan be ensured. Hence, in the fourth embodiment apparatus, when a typeof the PCBC is the LPBC in a case where it is determined that the AORCis being performed at a point in time when the performing condition forthe PCBC has been determined to be satisfied, the ACC is automaticallyresumed when the LPBC is finished.

According to the configuration above, when facing the avoidanceoperation necessary situation with a relatively low collision risk, adeceleration amount based on the brake operation by the driver can beensured due to the independent intervention in the brake control by thedriver, and thus a sufficient deceleration amount can be ensured bycombining this deceleration amount with a deceleration amount based onthe LPBC. Therefore, it becomes unnecessary to continue to stop the ACCfor a purpose of prompting the driver to intervene in the brake control.Thus, according to the configuration of the fourth embodiment apparatus,a deceleration amount can be sufficiently ensured in the avoidanceoperation necessary situation with the relatively low collision risk,and a possibility of giving a strange and annoying feeling to the driverstemmed from the ACC continuing to be stopped after the LPBC is finishedcontrary to the driver's expectation can be further reduced.

The vehicle control apparatuses according to the embodiments have beendescribed. However, the present disclosure is not limited to them andmay adopt various modifications within a scope of the presentdisclosure.

For example, the PCBC may be a control for applying a braking force withone stage or braking forces with more than or equal to three stages, inplace of a control with two stages. Besides, the PCBC may be a controlfor informing the driver of the brake operation being necessary byissuing a warning in addition to a control for applying the brakingforce.

Further, the above embodiments adopt a configuration where only the PBCis performed in a case of the high lap. However, a configuration is notlimited thereto. For example, a configuration where the LPBC isperformed in addition to the PBC in a case of the high lap may beadopted. In this case, the LPBC is performed when the TTC is more thanor equal to the first time threshold TTCth1 and less than apredetermined time threshold (>TTCth1) in a case of the high lap.

In addition, the second time threshold TTCth2 may be equal to the firsttime threshold TTCth1. Alternatively, the first time threshold TTCth1may not be constant, but change depending on the lap rate LR. Incontrast, the third time threshold TTCth3 may not change depending onthe lap rate LR, but be constant. In this case, the third time thresholdTTCth3 may be equal to the fourth time threshold TTCth4.

Further, the first time threshold TTCth1 may not be limited to the brakeavoidance limit time T_(B), but other time thresholds may be set as thefirst time threshold TTCth1. Similarly, the third time threshold TTCth3may not be limited to the steering avoidance limit time T_(S), but othertime thresholds may be set as the third time threshold TTCth3.

1. A vehicle control apparatus applied to an own vehicle comprising: anelectric control unit configured to: perform, as an adaptive cruisecontrol, a preceding vehicle trailing control which makes said ownvehicle trail a preceding vehicle which is a vehicle traveling ahead ofsaid own vehicle by calculating a target acceleration based on adistance to said preceding vehicle and a relative speed with respect tosaid preceding vehicle; perform an acceleration control for acceleratingsaid own vehicle and a deceleration control for decelerating said ownvehicle so that an acceleration of said own vehicle coincides with saidtarget acceleration; calculate a time-to-collision to a target objectpositioned in a predetermined region including a traveling direction ofsaid own vehicle based on a distance to said target object and arelative speed of said target object; and determine that a performingcondition for a first brake control which automatically applies apredetermined first braking force to said own vehicle is satisfied whensaid time-to-collision is less than a predetermined first threshold soas to perform said first brake control, wherein the electric controlunit is further configured to: continue performing said adaptive cruisecontrol when said deceleration control is being performed at a point intime when said performing condition for said first brake control hasbeen determined to be satisfied during a performance of said adaptivecruise control; stop performing said adaptive cruise control when saiddeceleration control is not being performed at said point in time; andnot to perform said first brake control when a performance of saidadaptive cruise control is continued in a case where said performingcondition for said first brake control is determined to be satisfiedduring a performance of said adaptive cruise control.
 2. The vehiclecontrol apparatus according to claim 1, wherein, said electric controlunit is configured to: perform, as said adaptive cruise control, anacceleration override control which accelerates said own vehicle inresponse to an accelerator operation by a driver of said own vehiclewhen a required acceleration based on said accelerator operation isgreater than said target acceleration, continue performing said adaptivecruise control when said acceleration override control is beingperformed at said point in time when said performing condition for saidfirst brake control has been determined to be satisfied during aperformance of said adaptive cruise control; and stop performing saidadaptive cruise control when said acceleration override control is notbeing performed at said point in time.
 3. The vehicle control apparatusaccording to claim 1, wherein, said electric control unit is configuredto: perform said first brake control when said time-to-collision is lessthan said first threshold and more than or equal to a second thresholdsmaller than said first threshold; determine that a performing conditionfor a second brake control which applies a second braking force greaterthan said first braking force to said own vehicle is satisfied when saidtime-to-collision is less than said second threshold so as to performsaid second brake control; and stop performing said adaptive cruisecontrol when said second brake control is started during a performanceof said adaptive cruise control.
 4. The vehicle control apparatusaccording to claim 3, wherein, said electric control unit is configuredto change said second threshold in a case when a target object, saidtime-to-collision thereof being less than said first threshold, is saidpreceding vehicle in such a manner that said second threshold becomessmaller as a lap rate becomes low, said lap rate being a value obtainedby dividing a length by which said own vehicle overlaps with saidpreceding vehicle in a vehicle width direction of said own vehicle whenassuming that said own vehicle collides with said preceding vehicle, bya vehicle width of said own vehicle.
 5. The vehicle control apparatusaccording to claim 2, wherein, said electric control unit is configuredto: perform said first brake control when said time-to-collision is lessthan said first threshold and more than or equal to a second thresholdsmaller than said first threshold; determine that a performing conditionfor a second brake control which applies a second braking force greaterthan said first braking force to said own vehicle is satisfied when saidtime-to-collision is less than said second threshold so as to performsaid second brake control; and stop performing said adaptive cruisecontrol when said second brake control is started during a performanceof said adaptive cruise control.
 6. The vehicle control apparatusaccording to claim 5, wherein, said electric control unit is configuredto change said second threshold in a case when a target object, saidtime-to-collision thereof being less than said first threshold, is saidpreceding vehicle in such a manner that said second threshold becomessmaller as a lap rate becomes low, said lap rate being a value obtainedby dividing a length by which said own vehicle overlaps with saidpreceding vehicle in a vehicle width direction of said own vehicle whenassuming that said own vehicle collides with said preceding vehicle, bya vehicle width of said own vehicle.
 7. A vehicle control apparatusapplied to an own vehicle comprising: an electric control unitconfigured to: perform, as an adaptive cruise control, a precedingvehicle trailing control which makes said own vehicle trail a precedingvehicle which is a vehicle traveling ahead of said own vehicle bycalculating a target acceleration based on a distance to said precedingvehicle and a relative speed with respect to said preceding vehicle;perform an acceleration control for accelerating said own vehicle and adeceleration control for decelerating said own vehicle so that anacceleration of said own vehicle coincides with said targetacceleration; calculate a time-to-collision to a target objectpositioned in a predetermined region including a traveling direction ofsaid own vehicle based on a distance to said target object and arelative speed of said target object; and determine that a performingcondition for a first brake control which automatically applies apredetermined first braking force to said own vehicle is satisfied whensaid time-to-collision is less than a predetermined first threshold soas to perform said first brake control, wherein said electric controlunit is further configured to: stop performing said adaptive cruisecontrol in a case where said first brake control is started during aperformance of said adaptive cruise control; and automatically resumesaid adaptive cruise control when said first brake control startedduring a performance of said adaptive cruise control is finished in acase where said deceleration control is being performed at a point intime when said performing condition for said first brake control hasbeen determined to be satisfied.
 8. The vehicle control apparatusaccording to claim 7, wherein, said electric control unit is configuredto: perform, as said adaptive cruise control, an acceleration overridecontrol which accelerates said own vehicle in response to an acceleratoroperation by a driver of said own vehicle when a required accelerationbased on said accelerator operation is greater than said targetacceleration; and automatically resume said adaptive cruise control whensaid first brake control started during a performance of said adaptivecruise control is finished in a case where said acceleration overridecontrol is being performed at said point in time when said performingcondition for said first brake control has been determined to besatisfied.
 9. The vehicle control apparatus according to claim 7,wherein, said electric control unit is configured to: perform said firstbrake control when said time-to-collision is less than said firstthreshold and more than or equal to a second threshold smaller than saidfirst threshold; determine that a performing condition for a secondbrake control which applies a second braking force greater than saidfirst braking force to said own vehicle is satisfied when saidtime-to-collision is less than said second threshold so as to performsaid second brake control; stop performing said adaptive cruise controlwhen said second brake control is started during a performance of saidadaptive cruise control; and continue stopping a performance of saidadaptive cruise control when said second brake control started during aperformance of said adaptive cruise control is finished.
 10. The vehiclecontrol apparatus according to claim 9, wherein, said electric controlunit is configured to change said second threshold in a case when atarget object, said time-to-collision thereof being less than said firstthreshold, is said preceding vehicle in such a manner that said secondthreshold becomes smaller as a lap rate becomes low, said lap rate beinga value obtained by dividing a length by which said own vehicle overlapswith said preceding vehicle in a vehicle width direction of said ownvehicle when assuming that said own vehicle collides with said precedingvehicle, by a vehicle width of said own vehicle.
 11. The vehicle controlapparatus according to claim 8, wherein, said electric control unit isconfigured to: perform said first brake control when saidtime-to-collision is less than said first threshold and more than orequal to a second threshold smaller than said first threshold; determinethat a performing condition for a second brake control which applies asecond braking force greater than said first braking force to said ownvehicle is satisfied when said time-to-collision is less than saidsecond threshold so as to perform said second brake control; stopperforming said adaptive cruise control when said second brake controlis started during a performance of said adaptive cruise control; andcontinue stopping a performance of said adaptive cruise control whensaid second brake control started during a performance of said adaptivecruise control is finished.
 12. The vehicle control apparatus accordingto claim 11, wherein, said electric control unit is configured to changesaid second threshold in a case when a target object, saidtime-to-collision thereof being less than said first threshold, is saidpreceding vehicle in such a manner that said second threshold becomessmaller as a lap rate becomes low, said lap rate being a value obtainedby dividing a length by which said own vehicle overlaps with saidpreceding vehicle in a vehicle width direction of said own vehicle whenassuming that said own vehicle collides with said preceding vehicle, bya vehicle width of said own vehicle.